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Diss Factsheets

Toxicological information

Skin sensitisation

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Administrative data

Endpoint:
skin sensitisation: in vivo (non-LLNA)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1995-08-02 to 1996-07-08
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1996
Report date:
1996

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 406 (Skin Sensitisation)
Version / remarks:
1992
GLP compliance:
yes
Type of study:
guinea pig maximisation test
Justification for non-LLNA method:
An LLNA study was not performed because there is an existing reliable study for skin sensitisation using the Guinea Pig Maximisation test method. Furthermore, the LLNA test method is not considered to be suitable for substances that contain silicon. Please refer to the attached document for further details.

Test material

Constituent 1
Chemical structure
Reference substance name:
Dimethylbis(octadecyloxy)silane
EC Number:
249-385-9
EC Name:
Dimethylbis(octadecyloxy)silane
Cas Number:
29043-70-7
Molecular formula:
C38H80O2Si
IUPAC Name:
dimethylbis(octadecyloxy)silane

In vivo test system

Test animals

Species:
guinea pig
Strain:
Dunkin-Hartley
Sex:
female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Italia S.p.A., Calco (Como), Italy.
- Age at study initiation: 4-6 weeks
- Weight at study initiation: 300-350 g
- Housing: groups of up to 5 animals in stainless steel cages (63x48x41 cm), with a grid floor. Cages were suspended over metal trays which held an absorbent material.
- Diet: ad libitum - commercially available laboratory diet (Altromin MSK, A. Rieper S.p.A., Bolzani, Italy)
- Water: ad libitum
- Acclimation period: at least 11 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24°C
- Humidity (%): 45-65%
- Air changes (per hr): no information given in study report
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 1995-10-26 To: 1995-12-07

Study design: in vivo (non-LLNA)

Inductionopen allclose all
Route:
intradermal
Vehicle:
other: Alembicol D
Concentration / amount:
10%
Route:
epicutaneous, occlusive
Vehicle:
other: Alembicol D
Concentration / amount:
75%
Challenge
No.:
#1
Route:
epicutaneous, occlusive
Vehicle:
other: Alembicol D
Concentration / amount:
50%
No. of animals per dose:
test group: 20; control group: 10
Details on study design:
RANGE FINDING TESTS:
Intradermal injection tolerance test: The hair over the scapulae was clipped and 0.1 ml of 50, 20, 10, 5, 1 and 0.1% of test substance in coconut oil were administered to 2 guinea pigs by intradermal injection. Erythema and eschar formation was scored using the Draize scoring scale seven days after injection. The highest concentration which was reasonably tolerated by the test system was selected for the intradermal induction stage of the main study.
Topical application tolerance test: The hair over the scapulae was clipped from 5 guinea pigs. Each animal was injected intradermally with 2 injections, each of 1 ml of emulsified Freund's adjuvant. 7 days later, the flanks were clipped and each animal was dosed with 2 concentrations of the test substance, one on each flank. A gauze patch was soaked with 0.2 ml of the selected concentration of the test substance and placed onto the selected treatment site. The sites were covered with a strip of aluminium foil to act as an occlusive barrier and the trunk of the animal was wrapped with an elastic adhesive bandage. Concentrations of 75, 50, 20, 10 and 5% of test substance in coconut oil were applied in duplicate. The dressings and patches were removed after 24h contact with the skin. Each site was assessed and scored. The highest reasonably achievable concentration which was tolerated by the test system, exhibiting no irritant response, was selected for the topical induction stage of the main study.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2
- Exposure period: Day 1 and 8
- Test groups: 3 pairs of 0.1 ml intradermal injections were made at the edge of the prepared site; the anterior (emulsified Freund's complete adjuvant) and median (10% test substance in coconut oil) injections were positioned close together and distant from the posterior (10% test substance in emulsified Freund's complete adjuvant) injections. Skin reaction at the injected sites was assessed approximately 24 hours after injection.
Six days after injection, animals were clipped and 0.5 ml of 10% sodium lauryl sulphate in petrolatum was spread evenly over the sites intended to enhance potential absorption of the test substance. On day 8 animals were treated with the 75% test substance. A gauze patch was covered with 0.4 ml of the substance and placed over the injection sites. This was covered with a strip of aluminium foil to serve as an occlusive barrier and the animal was wrapped with elastic adhesive bandage to maintain the patch in contact with the skin. Reaction to topical treatment was assessed approximately 24 hours after removal of dressing.
- Control group: Treated in the same manner as the test group on days 1 and 8 with the test substance being replaced by the vehicle alone. Skin reaction at the injected sites was assessed approximately 24 hours after injection. Reaction to topical treatment was assessed approximately 24 hours after dressing removal.
- Site: clipped scapular region over an area of approximately 2 0 x40 mm.
- Frequency of applications: a single induction by injection was followed on day 8 by a single topical induction.
- Duration: After a contact period of 48 hours the dressings were removed and the treated sites gently cleaned with warm water.
- Concentrations: 10% (intradermal), 75% (dermal)

B. CHALLENGE EXPOSURE
- No. of exposures: single exposure
- Day(s) of challenge: Day 22
- Exposure period: 24 hours
- Test groups: Patches of 20 x 20 mm gauze were soaked with 0.2 ml aliquots of 50% test substance and placed on the right flank of each animal in the centre of the prepared skin site. The left flank was similarly treated with patches soaked with 0.2 ml of coconut oil. The treated sites were covered with a strip of aluminium foil and wrapped with elastic adhesive bandage.
- Control group: Treated in the same manner as the test groups.
- Site: 50 x 50 mm clipped areas on flank
- Concentrations: 50%
- Evaluation (hr after challenge): 24 and 48 hours

OTHER: Freund's complete adjuvant (FCA), a mixture or paraffin oil, an emulsifier and killed mycobacteria, was used to enhance the potential of the substance to cause a delayed contact hypersensitivity reaction - used as a 50% v/v emulsion of FCA in sterile water. The test substance was mixed with the adjuvant prior to emulsification with sterile water.
Challenge controls:
The sensitivity of the guinea pig breed used for the sensitisation test was monitored; the last sensitivity test was carried out from 31 July to 21 August 1995.
Positive control substance(s):
yes
Remarks:
Benzocaine

Results and discussion

In vivo (non-LLNA)

Resultsopen allclose all
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
0%
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
Dose level:
0%
No. with + reactions:
0
Total no. in group:
10
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
24
Group:
negative control
Dose level:
50%
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
Dose level:
50%
No. with + reactions:
0
Total no. in group:
10
Remarks on result:
no indication of skin sensitisation
Reading:
1st reading
Hours after challenge:
24
Group:
test chemical
Dose level:
0%
No. with + reactions:
4
Total no. in group:
20
Remarks on result:
no indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
0%
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:
test chemical
Dose level:
50%
No. with + reactions:
2
Total no. in group:
20
Remarks on result:
no indication of skin sensitisation
Reading:
2nd reading
Hours after challenge:
48
Group:
test chemical
Dose level:
50%
No. with + reactions:
0
Total no. in group:
20
Remarks on result:
no indication of skin sensitisation
Reading:
other: challenge
Hours after challenge:
0
Group:
positive control
Dose level:
30% Benzocaine in petrolatum
No. with + reactions:
7
Total no. in group:
10
Remarks on result:
positive indication of skin sensitisation
Remarks:
70% response to 30% Benzocaine in petrolatum in rest group and 0% response in control group (number of animals not specified) in reliability check carried out July to August 1995

Any other information on results incl. tables

Some test group animals (2/20) had reactions at the vehicle application site and at the test substance (50%) application site, 24 hours after challenge exposure. There were no such observations after 48 hours. An additonal 2/20 animals in the test group had reactions at the vehicle application site only. Therefore, overall 4/20 animals in the test group had reactions to the vehicle, which were quickly reversed (by 48 hours). This was suggestive of an irritant effect of the vehicle.

Control animals did not have any reactions at 24 or 48 hours after challenge exposure.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
Dimethylbis(octadecyloxy)silane has been tested for in a guinea pig maximisation study using the method of Magnusson and Kligman in a study conducted according to OECD TG 406 and in compliance with GLP. Two weeks after the induction phase of a single intradermal injection of 10% test substance in Alembicol D with and without Freund's adjuvant followed one week later by occlusive application of 75% test substance in Alembicol D the animals were challenged with a 50% solution of test substance in the same vehicle. In the test group, mild reactions to test substance (50% in vehicle) were observed in 2/20 animals and to vehicle alone in a further 2/20 test animals at the 24 hour observation; these were fully resolved by the 48 hour observation. No reactions were observed in any of the 10 negative control animals. It was concluded that the observed effects indicated a mild skin irritation reaction to the vehicle and the test substance was not sensitising to skin.