Registration Dossier

Administrative data

Description of key information

Skin sensitisation:

Weight of evidence: Despite of being in wide dispersive use for years, only a few cases of skin sensitization due to BHT as ingredient of various products are discussed. Signs of contact dermatitis after dermal exposure to BHT were occasionally reported (Flyvholm & Menne 1990). In another report (Goodman et al. 1990), two patients with chronic idiopathic urticaria developed exacerbations when challenged with BHT/BHA, but had less symptoms after consuming a BHT/BHA-free diet. When patch tested on more than 15 individuals, BHT showed mild skin irritation; a positive skin reaction 14 days later was interpreted as sensitization (Mallette & von Haam 1952). However, these limited reports do not allow drawing any conclusions as to the skin irritation and sensitization of BHT in view of the widespread exposure to BHT in consumer products. There are some more recent patch test results obtained from the medical surveillance of great numbers of workers (de Boer et al. 1989; Goh & Ho 1993) or patients (Kanerva et al. 1997; 1999) which were all negative. A multicenter patch-test study by Schnuch (1998) showed that BHT provoked positive skin reactions in only 11/11454 patients.

Read-across approach:

The analogue CAS No. 118-82-1 (2,2',6,6'-tetra-tert-butyl-4,4'-methylenediphenol)which shares the same functional group (alkylphenol) with the substance CAS no. 128-37-0 (2,6-di-tert-butyl-p-cresol), also has comparable values for the relevant molecular properties. Therefore, the results obtained with the substance CAS No. 118-82-1 can be used for the read-across approach.

In the guinea-pig maximization test of Magnusson and Kligman, none of the twenty test animals showed positive responses at 24 or 48 hours after removal of the challenge patches. The test material (source chemical) was therefore not a skin sensitizer in guinea pigs. By applying the read across approach, the target chemical BHT is not considered a skin sensitizer in guinea pigs.

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Referenceopen allclose all

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Although the study was not conducted according to the recommended guidelines, it provides scientific valid information to assess the allergic patch reations to the substance.
Principles of method if other than guideline:
Patch tests were performed on 40 metalworkers. Each worker received patch tests with several dilutions of the metalworking fluid to which he was exposed and also with own products such as soaps and creams. The materials were applied to the upper back using Van der Bend Square Chambers and fixed with Fixomull tape. The patches were removed at 48 h and scored at 72 h.
GLP compliance:
not specified
Type of study:
patch test
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Sex:
not specified
Details on test animals and environmental conditions:
Patch tests were performed on 40 metalworkers.
Key result
Reading:
other:
Hours after challenge:
72
Group:
test group
Dose level:
2 %
No. with + reactions:
0
Total no. in group:
40
Remarks on result:
other: Existing information of human exposure
Remarks:
Patch test

BHT was applied at a concentration of 2% (vehicle: pet.) and the patch tests were negative.

Interpretation of results:
GHS criteria not met
Remarks:
Migrated information
Conclusions:
BHT was applied at a concentration of 2% (vehicle: pet.) and the patch tests were negative.
Executive summary:

Patch tests were performed on 40 metalworkers. Each worker received patch tests with several dilutions of the metalworking fluid to which he was exposed and also with own products such as soaps and creams. The materials were applied to the upper back using Van der Bend Square Chambers and fixed with Fixomull tape. The patches were removed at 48 h and scored at 72 h. BHT was applied at a concentration of 2% (vehicle: pet.) and the patch tests were negative.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Although the study was not conducted according to the recommended guidelines, it provides scientific valid information to assess the allergic patch reations to the substance.
Principles of method if other than guideline:
The study included 1336 consecutive patients, all new referrals with eczema patch tested from September 1987 to December 1989. Patch tests were performed with the European standard series, supplemented with BHT 2%. Finn Chambers applied with Scanpor were used. The tests were left on the skin for 2 days and readings were performed after 2 days, 3 days and 1 week.
GLP compliance:
not specified
Type of study:
patch test
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Sex:
male/female
Details on test animals and environmental conditions:
The study included 1336 consecutive patients, all new referrals with eczema patch tested from September 1987 to December 1989.
Key result
No. with + reactions:
0
Total no. in group:
1 369
Remarks on result:
other: Existing information of human exposure
Remarks:
Patch test

For a 2 -year period, 1336 consecutive patients were patch tested with BHT. All patch tests were negative.

Interpretation of results:
GHS criteria not met
Conclusions:
For a 2 -year period, 1336 consecutive patients were patch tested with BHT. All patch tests were negative.
Executive summary:

The study included 1336 consecutive patients, all new referrals with eczema patch tested from September 1987 to December 1989. Patch tests were performed with the European standard series, supplemented wth BHT 2%. Finn Chambers applied with Scanpor were used. The tests were left on the skin for 2 days and readings were performed after 2 days, 3 days and 1 week.All patch tests were negative.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Patch tests results on machinists using dielectric fluid containing BHT.
Principles of method if other than guideline:
Machinists using dielectric fluid in a factory were patch tested to the dielectric fluid 5% in acetone and 10% acetone butylated hydroxytoluene 2% pet. and Rozalex barrier cream and Achron hand cleanser 5% pet.
GLP compliance:
no
Type of study:
patch test
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Key result
Remarks on result:
other: Existing information of human exposure.
Remarks:
See summary

All machinists showed an irritant reaction to the dielectric fluid (non-palpable faint to moderate erythema to dielectric fluid 5% acetone and in 5, erosive erythema to dielectric fluid 10% acetone). 5 machinists with the hand eczema were investigated at the skin clinic and had patch tests to the European standard series in addition, all were negative except for one with a positive reaction to nickel which was of past relevance. Based on the clinical findings and non-allergic patch test results, all machinists were diagnosed as having irritant contact dermatitis from the dielectric fluid.

Interpretation of results:
study cannot be used for classification
Conclusions:
Based on the clinical findings and non-allergic patch test results, all machinists were diagnosed as having irritant contact dermatitis from the dielectric fluid.
Executive summary:

Machinists using dielectric fluid in a factory were patch tested to the dielectric fluid containing BHT. All machinists showed an irritant reaction to the dielectric fluid (non-palpable faint to moderate erythema to dielectric fluid 5% acetone and in 5, erosive erythema to dielectric fluid 10% acetone). 5 machinists with the hand eczema were investigated at the skin clinic and had patch tests to the European standard series in addition, all were negative except for one with a positive reaction to nickel which was of past relevance. Based on the clinical findings and non-allergic patch test results, all machinists were diagnosed as having irritant contact dermatitis from the dielectric fluid.

Endpoint:
skin sensitisation
Remarks:
in vivo
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Information on response of two patients with chronic urticaria when challenged with BHT/BHA.
Principles of method if other than guideline:
Response of two patients with chronic urticaria when challenged with BHT.
GLP compliance:
no
Type of study:
other: response of two patients with chronic urticaria when challenged with BHT.
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Sex:
male
Details on test animals and environmental conditions:
Two patients with chronic urticaria.
Key result
Remarks on result:
other: Existing information of human exposure
Remarks:
See executive summary

Positive reactions to the BHT/BHA challenge doses occurred in the patients between 1 and 6 hours after ingestion. Although this temporal sequence is not inconsistent with that observed with adverse (e.g., urticarial) reactions to ingested foods, the longer interval to symptom onset would possibly diminish awareness of potential causality in a patient unsuspecting of the source of the exacerbant. The diet content of BHA/BHT may be less than the amounts used in our challenge sequence. It may be reasonably expected that "natural" dietary exposures to the additives at these lower levels might not be as readily perceived by the patient as being potentially related to exacerbations of their urticaria.

Conclusions:
Two patients with chronic idiopathic urticaria developed exacerbations when challenged with BHT/BHA, but had less symptoms after consuming a BHT/BHA-free diet.
Executive summary:

BHT/BHA was provided for patient No.1 in clear gelatin capsules. For patient No. 2, challenge powders were provided in grey opaque gelatin capsules. After a minimum 6-hour ovemight fast, the patients ingested the first challenge dose. This dose was followed by the second, larger dose 2 to 4 hours later, assuming that no major exacerbation of symptoms had occurred in this time frame. Challenges proceeded on daily intervals unless there was a positive reaction; in that case, 24 to 48 hours was allowed to elapse before the next challenge to allow the reaction to retum to baseline and to avoid false negatives caused by a refractory period, as reported for aspirin challenges. BHA and BHT were administered simultaneously, with the initial dose including 125 mg of each and the second dose including 250 mg of each. Positive reactions to the BHT/BHA challenge doses occurred in the patients between 1 and 6 hours after ingestion. Although this temporal sequence is not inconsistent with that observed with adverse (e.g., urticarial) reactions to ingested foods, the longer interval to symptom onset would possibly diminish awareness of potential causality in a patient unsuspecting of the source of the exacerbant. The diet content of BHA/BHT may be less than the amounts used in our challenge sequence. It may be reasonably expected that "natural" dietary exposures to the additives at these lower levels might not be as readily perceived by the patient as being potentially related to exacerbations of their urticaria.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Although the study was not conducted according to the recommended guidelines, it provides scientific valid information to assess the allergic patch test reactions to the substance.
Principles of method if other than guideline:
Most of the patients are referred because of suspected occupational dermatoses and they are patch tested with a modified European standard series, and their own substances. Patch testing was performed with 2 days occlusion and 3 readings (usually on days 2, 3 and 4-6). Allergic reactions were scored according to ICDRG recommendations. Irritant reactions were also recorded. Data was compiled for 3 years.
GLP compliance:
not specified
Type of study:
patch test
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Sex:
male/female
Details on test animals and environmental conditions:
173 patients (3-year period)
Key result
Remarks on result:
other: Existing information of human exposure
Remarks:
Patch test data, see executive summary

No allergic reactions were observed for BHT.

Interpretation of results:
GHS criteria not met
Remarks:
Migrated information
Conclusions:
No allergic reactions were observed for BHT.
Executive summary:

Most of the patients are referred because of suspected occupational dermatoses and they are patch tested with a modified European standard series, and their own substances. Patch testing was performed with 2 days occlusion and 3 readings (usually on days 2, 3 and 4-6). The patch concentration for BHT was 2% (w/w). Allergic reactions were scored according to ICDRG recommendations. Irritant reactions were also recorded. Data was compiled for 3 years.No allergic reactions were observed for BHT.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Remarks:
Although the study was not conducted according to the recommended guidelines, it provides scientific valid information to assess the allergic patch reations to the substance.
Principles of method if other than guideline:
Most of the patients are remitted because of a suspected occupational skin disease. They are usually patch-tested with a modified European standard series, other relevant series related to their work or hobbies and their own substances. Data was compiled during 6 years. Patch testing was performed with 2 days occlusion and 3 readings (usually on days 2, 3 and 4-6). Allergic reactions were scored according to ICDRG recommendations. Irritant reactions were also recorded.
GLP compliance:
not specified
Type of study:
patch test
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Sex:
male/female
Details on test animals and environmental conditions:
358 patients (6-year period)
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
test group
No. with + reactions:
0
Total no. in group:
358
Remarks on result:
other: Patch test
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
test group
No. with + reactions:
0
Total no. in group:
358
Remarks on result:
other: Patch test
Key result
Reading:
other: 3rd reading
Hours after challenge:
96
Group:
test group
No. with + reactions:
0
Total no. in group:
358
Remarks on result:
other: The 3rd reading was conducted on day 4 to 6after induction
Remarks:
(Patch test)

No allergic reactions were observed for BHT.

Interpretation of results:
GHS criteria not met
Conclusions:
No allergic reactions were observed for BHT.
Executive summary:

Most of the patients are remitted because of a suspected occupational skin disease. They are usually patch-tested with a modified European standard series, other relevant series related to their work or hobbies and their own substances. Data was compiled during 6 years. Patch testing was performed with 2 days occlusion and 3 readings (usually on days 2, 3 and 4-6). Allergic reactions were scored according to ICDRG recommendations. Irritant reactions were also recorded. The patch concentration for BHT was 2% (w/w). No allergic reactions were observed for BHT.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
unsuitable test system
Remarks:
Only one case is reported and it is not well documented.
Principles of method if other than guideline:
One case of allergic contact dermatitis from rubber footwear was investigated by patch testing.
GLP compliance:
no
Type of study:
patch test
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Key result
No. with + reactions:
0
Total no. in group:
1
Remarks on result:
other: Existing information of human exposure
Remarks:
Patch test

One case of allergic contact dermatitis from rubber footwear was investigated by patch testing. The patient did not reacted to BHT.

Interpretation of results:
study cannot be used for classification
Conclusions:
One case of allergic contact dermatitis from rubber footwear was investigated by patch testing. The patient did not reacted to BHT.
Executive summary:

One case of allergic contact dermatitis from rubber footwear was investigated by patch testing. The patient did not reacted to BHT.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
unsuitable test system
Remarks:
Only one case is reported and it is not well documented.
Principles of method if other than guideline:
A 37-year old woman, with no past history of allergy, had developed an itchy inflammatory oedema of her scalp and face with occipital lymph node swelling one day after the second application of a new hair-colouring preparation. Patch tests were then performed with the 20 ingredients of the hair dye at their use concentration.
GLP compliance:
no
Type of study:
patch test
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Sex:
female
Key result
Hours after challenge:
24
No. with + reactions:
1
Total no. in group:
1
Clinical observations:
Itchy inflammatory oedema of scalp and face with occipital lymph node with swelling
Remarks on result:
other: Existing information of human exposure.
Remarks:
See summary

A strongly positive reaction to tertiary-butylhydroquinone (TBHQ) was observed. BHT at 1% pet. produced positive reactions at day 2 and day 4.

Interpretation of results:
study cannot be used for classification
Conclusions:
A strongly positive reaction to tertiary-butylhydroquinone (TBHQ) was observed. BHT at 1% pet. produced positive reactions at day 2 and day 4.
Executive summary:

A 37-year old woman, with no past history of allergy, had developed an itchy inflammatory oedema of her scalp and face with occipital lymph node swelling one day after the second application of a new hair-colouring preparation. Patch tests were then performed with the 20 ingredients of the hair dye at their use concentration. A strongly positive reaction to tertiary-butylhydroquinone (TBHQ) was observed. BHT at 1% pet. produced positive reactions at day 2 and day 4. Cross-reactions seem possible between TBHQ and BHA and even BHT.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Remarks:
Not well documented. However, it provides evidences to be taken into account for the weight of evidence analysis.
Principles of method if other than guideline:
Not less than 15 individuals are tested with BHT which is placed by patch on the skin of the back and remains for 48 hours. The sensitising effect of the substance is determined by reapplying the material to the skin after a waiting period of 14 days. Light reaction consists of a faint pinkish discoloration of the skin with slight scaling at late observation. A moderate reaction consists of a dull-red discoloration with edema, slight maceration, and possibly small petechiae. A severe reaction consists of a painful hemorrhagic inflammatory reaction followed by central necrosis and ulceration.
GLP compliance:
no
Type of study:
patch test
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Sex:
not specified
Key result
Dose level:
100 %
No. with + reactions:
4
Total no. in group:
15
Remarks on result:
other: Existing information of human exposure (Patch test)
Remarks:
29 % of subjects had light reactions and 0 % severe reactions

The results showed a 71% of negative reactions, 29% of light reactions and 0% of severe reactions. The authors considered that the substance presented a moderate sensitising effect.

Conclusions:
The results showed a 71% of negative reactions, 29% of light reactions and 0% of severe reactions. The authors considered that the substance presented a moderate sensitising effect.
Executive summary:

Not less than 15 individuals are tested with BHT (100% concentration) which is placed by patch on the skin of the back and remains for 48 hours. The sensitising effect of the substance is determined by reapplying the material to the skin after a waiting period of 14 days. Light reaction consists of a faint pinkish discoloration of the skin with slight scaling at late observation. A moderate reaction consists of a dull-red discoloration with edema, slight maceration, and possibly small petechiae. A severe reaction consists of a painful hemorrhagic inflammatory reaction followed by central necrosis and ulceration. The results showed a 71% of negative reactions, 29% of light reactions and 0% of severe reactions. The authors considered that the substance presented a moderate sensitising effect.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: Not well documented. However, it provides evidences to be taken into account for the weight of evidence analysis.
Principles of method if other than guideline:
Patch tests using two methods were carried out. In the first method patients with suspected contact dermatitis are exposed for two days and the first reading is conducted at 2 days and the second reading at 3-4 days. In the second method the patients were exposed for 3 days and read 3 h after the removal of the substance.
GLP compliance:
no
Type of study:
patch test
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Sex:
male/female
Key result
Group:
test group
No. with + reactions:
1
Total no. in group:
155
Remarks on result:
other: Existing information of human exposure
Remarks:
First method
Key result
Group:
test group
No. with + reactions:
2
Total no. in group:
155
Remarks on result:
other: Existing information of human exposure
Remarks:
Second method

Following the first procedure, 1/155 patients reacted positive to BHT. Using the second procedure, 2/155 patients were positive.

Conclusions:
Following the first procedure, 1/155 patients reacted positive to BHT. Using the second procedure, 2/155 patients were positive.
Executive summary:

Patch tests using two methods were carried out. In the first method patients with suspected contact dermatitis are exposed for two days and the first reading is conducted at 2 days and the second reading at 3-4 days. In the second method the patients were exposed for 3 days and read 3 h after the removal of the substance. Following the first procedure, 1/155 patients reacted positive to BHT. Using the second procedure, 2/155 patients were positive.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The sensitivity and reliability of the experimental technique was not assessed by use of substances which are known to have mild-to-moderate skin sensitisation properties. However, it is considered that this deviation does not affect the outcome of the study.
Qualifier:
according to
Guideline:
other: Magnusson and Kligman (1969)
Deviations:
yes
Remarks:
(However, it is considered that this deviation does not affect the outcome of the study)
GLP compliance:
yes
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
The study was conducted in 1988, the regulatory field was different.
Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Porcellus Ltd., U.K.
- Age at study initiation: Not documented.
- Weight at study initiation: males: 558-667 g; females: 501-565 g
- Housing: Animals were housed in groups of five animals (two and three per cage). Hanging, stainless-steel cages with all-mesh floors and tops and half-mesh fronts were used. Each cage measured 54 cm x 31 cm x 36 cm.
- Diet (e.g. ad libitum): SG1 with vitamin C supplement, Grain Harvesters Ltd., Kent, ad libitum.
- Water (e.g. ad libitum): Filtered from public supply, ad libitum.
- Acclimation period: At least two weeks.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-23 ºC
- Humidity (%): Not documented.
- Air changes (per hr): Not documented.
- Photoperiod (hrs dark / hrs light): Lighting was automatically switched on for the day (06.00 to 18.00 hours GMT) and off for the night (18.00 to 06.00 hours GMT).


Route:
intradermal
Vehicle:
corn oil
Concentration / amount:
Test animals: 0.5 % m/v:
Anterior sites: 0.1 ml of Freunds Complete Adjuvant (FCA)
Middle sites: 0.1 ml of test material in corn oil
Posterior sites: 0.1 ml of test material in 50:50 FCA/corn oil
Route:
intradermal
Vehicle:
corn oil
Concentration / amount:
Control animals:
Anterior sites: 0.1 ml of FCA
Middle sites: 0.1 ml of corn oil
Posterior sites: 0.1 ml of 50:50 FCA/corn oil
Route:
epicutaneous, occlusive
Vehicle:
other: Petroleum jelly
Concentration / amount:
0.45 mL of diluted test material (50 % m/m)
Day(s)/duration:
48 hours
Adequacy of induction:
other: The epicutaneous induction was conducted one week after intradermal injections.
No.:
#1
Route:
epicutaneous, occlusive
Vehicle:
corn oil
Concentration / amount:
0.15 mL of the diluted test material (50% m/m in petroleum jelly).
Day(s)/duration:
24 hours
Adequacy of challenge:
other: 14 days after the epicutaneous induction
No. of animals per dose:
Ten animals per sex.
Control group: five animals per sex.
Details on study design:
RANGE FINDING TESTS:
Two male and two female guinea pigs were closely shorn in the shoulder region using electric clippers followed by an electric razor. 0.1 ml doses of several dilutions (0.05, 0.1, 0.5 and 1.0% m/v in corn oil) of the test material were injected intradermally on each side of the mid-line. The animals were examined to determine the maximum concentration that could be used without causing untoward toxicity.

The flanks of each animal in further groups of two male and two female guinea pigs was closely shorn. 0.3 ml doses of several dilutions (25% and 50 m/m in petroleum jelly) of the test material were absorbed onto 16 cm2 Whatman No. 3 filter paper patches. The patches were placed on the flanks and held in place with a “Sleek” adhesive tape patch, then covered with an 8 cm “Poroplast” elastic adhesive bandage for 24 hours. After removal of the patches and bandages the dermal test sites were examined for signs of irritation.

MAIN STUDY
A. INDUCTION EXPOSURE
Pairs of intradermal injections were administered to the animals as described under the heading "concentration". One week after induction by intradermal injection, the same area of skin was shaven using electric clippers. A 16 cm2 patch of Whatman No. 3 filter paper was coated with 0.45 ml of the test material and placed over the sites of intradermal injections. The patches were covered with a “Sleek” dressing. The dressing was then securely covered with an 8 cm “Poroplast” elastic adhesive bandage for 48 hours.


B. CHALLENGE EXPOSURE
Challenge was carried out two weeks after the topical induction. Hair was removed from a 3 cm x 3 cm area of one flank by clipping then shaving. A 4cm2 patch of Whatman No. 3 filter paper coated with 0.15 ml of the test material was placed on the shaven area, covered with a 3 cm square of adhesive tape, held in place by an 8 cm “Poroplast” elastic adhesive bandage. After 24 hours the patches were removed and the challenges sites examined for any response, 24 and 48 hours after its removal.
Challenge controls:
Controls were also treated with the test material.
Positive control substance(s):
no
Key result
Reading:
1st reading
Hours after challenge:
24
Group:
test group
No. with + reactions:
0
Total no. in group:
20
Remarks on result:
no indication of skin sensitisation
Key result
Reading:
2nd reading
Hours after challenge:
48
Group:
test group
No. with + reactions:
0
Total no. in group:
20
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
No. with + reactions:
0
Total no. in group:
10
Remarks on result:
no indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
negative control
No. with + reactions:
0
Total no. in group:
10
Remarks on result:
no indication of skin sensitisation

Table 7.4.1: Summary of the Sensitisation Response after Challenge

Sensitisation Response

Hours

24

48

Test animals

0/20

0/20

Control animals

0/10

0/10

Interpretation of results:
GHS criteria not met
Conclusions:
In the guinea-pig maximization test of Magnusson and Kligman, none of the twenty test animals showed positive responses at 24 or 48 hours after removal of the challenge patches. The test material was therefore not a skin sensitizer in guinea pigs.
Executive summary:

A range-finding test was performed to determine the appropriate concentrations that could be used for both intradermal and topical induction as well as topical challenge. The first induction phase involved six intradermal injections. These doses were comprised of pairs of injections of the test substance in corn oil, the test substance combined with Complete Freund´s Adjuvant and corn oil and the Adjuvant alone. A control group (ten animals) was maintained under the same environmental conditions and received injections of corn oil, corn oil combined with complete Freund´s Adjuvant and Adjuvant alone. The second phase of induction was conducted by topical application for a period of 48 hours. Two weeks after the topical induction, a challenge dose of the test material was applied for 24 hours. Twenty-four and 48 hours after challenge patch removal, the animals were scored for a sensitisation response. None of the twenty test animals showed any positive response at either 24 or 48 hours after removal of the challenge patches.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
weight of evidence
Reliability:
3 (not reliable)
Rationale for reliability incl. deficiencies:
other: Not well documented (few data on methodology and no data on time of exposure for BHT). However, it provides evidences to be taken into account for the weight of evidence analysis.
Remarks:
i
Principles of method if other than guideline:
Patch tests were performed according to recommendations of the International Contact Dermatitis Research Group and the German Contact Dermatitis Group.
GLP compliance:
no
Type of study:
patch test
Justification for non-LLNA method:
Existing information of human exposure.
Species:
human
Sex:
male/female
Vehicle:
petrolatum
Vehicle:
petrolatum
Key result
Reading:
1st reading
Group:
test group
Dose level:
2.0 %
No. with + reactions:
11
Total no. in group:
11 454
Remarks on result:
other: Existing information of human exposure
Remarks:
Patch test
Key result
Reading:
1st reading
Group:
test group
Dose level:
2.0 %
No. with + reactions:
51
Total no. in group:
11 454
Clinical observations:
Questionable irritative response
Remarks on result:
other: Existing information of human exposure
Remarks:
Patch test

The study is a multicenter study; 9/24 centers applied patch test for 24 hours, the remainder (15/24) for 48 hours.
For the study only readings at 72 hours after the application of test chambers were considered.

The results indicated that 11/11454 patients showed a positive reaction with BHT and 51/11454 patients showed a questionable irritative response.

Conclusions:
The results indicated that 11/11454 patients showed a positive reaction with BHT and 51/11454 patients showed a questionable irritative response.
Executive summary:

Patch tests were conducted in patients with suspected allergic contact dermatitis. Butylhydroxytoluol was applied as a test preparation of 2.0% in petrolatum. The results indicated that 11/11454 patients showed a positive reaction with BHT and 51/11454 patients showed a questionable irritative response.

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: 'Read-across from an analogue substance for which a guideline study (Klimisch 2) is available.
Reason / purpose:
read-across source
Principles of method if other than guideline:
Read-across from company data on an analogue
GLP compliance:
yes
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
There is existing information on an analogue chemical which can be used in a read across approach.
Key result
Remarks on result:
other: Read across
Remarks:
See cross reference to source information
Interpretation of results:
GHS criteria not met
Conclusions:
In the guinea-pig maximization test of Magnusson and Kligman, none of the twenty test animals showed positive responses at 24 or 48 hours after removal of the challenge patches. The test material (source chemical) was therefore not a skin sensitizer in guinea pigs. By applying the read across approach, the target chemical BHT is not considered a skin sensitizer in guinea pigs.
Executive summary:

The analogue CAS No. 118-82-1 (2,2',6,6'-tetra-tert-butyl-4,4'-methylenediphenol) which shares the same functional group (alkylphenol) with the substance CAS no. 128-37-0 (2,6-di-tert-butyl-p-cresol), also has comparable values for the relevant molecular properties. Therefore, the results obtained with the substance CAS No. 118-82-1 can be used for the read-across approach.

Based on company data, the read-across approach is applied from the source chemical 2,2',6,6'-tetra-tert-butyl-4,4'-methylenediphenol to the target chemical 2,6 -di-tert-butyl-p-cresol (BHT) and the target is not considered to be a skin sensitiser.

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)

Respiratory sensitisation

Endpoint conclusion
Endpoint conclusion:
no study available

Justification for classification or non-classification

Based on the available data, the substance is not classified as skin sensitiser according to CLP Regulation.