Isopentyl p-methoxycinnamate

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Link to relevant study records

Reference

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1994-12-8 to 1995-01-08

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Deviations:

no

Principles of method if other than guideline:

not applicable

GLP compliance:

yes (incl. QA statement)

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

Existing data is available from a guinea pig maximisation test, new in vivo testing has not been conducted for the purposes of REACH registration

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

not specified

Details on test animals and environmental conditions:

At the start of the main study, the animals weighed 339 - 449 g, and were approximately eight to twelve weeks old. After a minimum acclimatisation period of 5 d, each animal was selected at random and given a unique number.
The animals were housed singly or in pairs in solid-floor polypropylene cages furnished with woodflakes. Free access to mains tap water and food (Guinea pig FD1 Diet, Special Diets Services Limited, Witham, Essex, U.K.) was allowed throughout the study.
The animal room was maintained at a temperature of 18-22°C and relative humidity of 41-64 %. The rate of air exchange was approximately 15 changes per h and the lighting was controlled by a time switch to give 12 h light and 12 h darkness.

Route:

intradermal and epicutaneous

Vehicle:

arachis oil

Concentration / amount:

Intradermal induction: 5% w/v in arachis oil B.P. and 5% w/v in a mixture of Freund's Complete Adjuvants plus distilled water (1:1)
Topical induction: undiluted as supplied
Topical challenge: undiluted as supplied and 75% v/v in 1:1 ethanol/diethylphthalate

Route:

epicutaneous, occlusive

Vehicle:

arachis oil

Concentration / amount:

Intradermal induction: 5% w/v in arachis oil B.P. and 5% w/v in a mixture of Freund's Complete Adjuvants plus distilled water (1:1)
Topical induction: undiluted as supplied
Topical challenge: undiluted as supplied and 75% v/v in 1:1 ethanol/diethylphthalate

No. of animals per dose:

A group of 30 guinea pigs was used for the main study, twenty test and ten control animals.

Details on study design:

Induction =Shortly before treatment on Day 0, the hair was removed from an area approximately 40 mm x 60 mm on the shoulder region of each animal with veterinary clippers. A row of three injections (0.1 mL each) was made on each side of the mid-line. The injections were:
i) Freund's Complete Adjuvants plus distilled water in the ratio 1:1
ii) a 5% w/v dilution of test material in arachis oil B.P.
iii) a 5% w/v diltuion of test material in a 1:1 preparation of Freund's Complete Adjuvants plus distilled water
Approximately 24 and 48 h after intradermal injection the degree of erythema at the test material injection sites was evaluated.
One week later (day 7), the same area on the shoulder region used previously for intradermal injections was clipped again and treated with a topical application of the undiluted test material. The undiluted test material was applied to saturation on filter paper whih was held in place by a strip of surgical tape and covered with an overlapping lenght of aluminium foil. The patch and foil were further secured by a strip of elastic adhesive bandage wound in a double layer around the torso of each animal. This occlusive dressing was kept in place for 48 h.
The degree of erythema and oedema was quantified one and 24 h following removal of the patches.

Induction of the control animals= intradermal injections were administered using an identical procedure to that used for the test animals, except that the injections were:
i) Freund's Complete Adjuvants plus distilled water in the ratio 1:1
ii) Arachis oil B.P.
iii) 50 % w/v formulation of arachis oil B.P. in a 1:1 mixture of Freund's Complete Adjuvants/ distilled water
The topical applications followed the same procedure as for the test animals except that nothing was applied to the filter paper. Skin reactions were auantified as for the test animals.

Challenge controls:

Shortly before treatment on Day 21, an area, approximately 50 mm x 70 mm on both flanks of each animal, was clipped free of hair with veterinary clippers.
A quantity of the undiluted test material was applied to saturation to the shorn right flank of each animal on a square of filter paper which was held in place by a strip of surgical adhesive tape. To ensure that the maximum non-irritant concentration was used as challenge, the test material (at a concentration of 75 % v/v in 1:1 ethanol/ diethylphthalate) was applied similarly to a skin site on the left shorn flank. The patches were occluded with an overlapping lenght of aluminium foil and secured by a strip of elastic adhesive bandage wound in a double layer around the torso of each animal.
After 24 h, the dressing was carefully cut using blunt-tipped scissors, removed, and discarded. The challenged sites were swabbed with cotton wool soaked in diethyl ether to remove residual material. Approximately 24 and 48 h after challenge dressing removal, the degree of erythema and oedema formation was quantified.

Positive control substance(s):

not specified

Positive control results:

no positive controls

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

Undiluted

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

No skin reactions

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: Undiluted. No with. + reactions: 0.0. Total no. in groups: 20.0. Clinical observations: No skin reactions.

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

Undiluted

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No skin reactions

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: Undiluted. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: No skin reactions.

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

Undiluted

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

No skin reactions

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: Undiluted. No with. + reactions: 0.0. Total no. in groups: 20.0. Clinical observations: No skin reactions.

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

Undiluted

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No skin reactions

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: Undiluted. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: No skin reactions.

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

75 % v/v in 1:1 Ethanol/diethylphthalate

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

No skin reactions

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: test group. Dose level: 75 % v/v in 1:1 Ethanol/diethylphthalate. No with. + reactions: 0.0. Total no. in groups: 20.0. Clinical observations: No skin reactions.

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

75 % v/v in 1:1 Ethanol/diethylphthalate

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No skin reactions

Remarks on result:

other: Reading: 1st reading. . Hours after challenge: 24.0. Group: negative control. Dose level: 75 % v/v in 1:1 Ethanol/diethylphthalate. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: No skin reactions.

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

75 % v/v in 1:1 Ethanol/diethylphthalate

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

No skin reactions

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: test group. Dose level: 75 % v/v in 1:1 Ethanol/diethylphthalate. No with. + reactions: 0.0. Total no. in groups: 20.0. Clinical observations: No skin reactions.

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

75 % v/v in 1:1 Ethanol/diethylphthalate

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

No skin reactions

Remarks on result:

other: Reading: 2nd reading. . Hours after challenge: 48.0. Group: negative control. Dose level: 75 % v/v in 1:1 Ethanol/diethylphthalate. No with. + reactions: 0.0. Total no. in groups: 10.0. Clinical observations: No skin reactions.

not applicable

Interpretation of results:

GHS criteria not met

Conclusions:

The test material was classified as a non-sensitiser to guinea pig skin. The test material did not meet the criteria for classification as a sensitiser according to EC labelling regulations. No risk phrase is required.

Executive summary:

A guinea pig maximisation test was performed to assess the skin contact sensitisation potential of the test material in albino guinea pigs. The method used followed the one described in the current OECD guidelines no. 406 "Skin sensitisation" and the method B.6 of Commission Directive 92/69/EEC.

Twenty test and ten control animals were used for the main study.

Based on the results of sighting tests, the concentrations of test material for the inducton and challenges phases were selected as follows:

Intradermal induction	5% w/v in arachis oil B.P.
Topical induction	undiluted as supplied
Topical challenge	undiluted as supplied and 75% v/v in 1:1 ethanol/diethylphthalate

The test material produced a 0% (0/20) sensitisation rate and was classified as a non-sensitiser to guinea pig skin. The test material did not meet the criteria for classification as a sensitiser according to EC labelling regulations. No risk phrase is required.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

When tested in a guinea pig maximisation test in Dunkin-Hartley guinea pigs at the concentrations given above, isopentyl p-methoxycinnamate did not induce skin sensitisation in any of the test animals. Accordingly, isopentyl p-methoxycinnamate was classified as a non-sensitiser to guinea pig skin.

Additional information on the sensitising and photosensitising potential of isopentyl p-methoxycinamate is available from 3 recently conducted patch tests in humans (Cardoso et al. 2009; Chew et al. 2010; Pentinga et al. 2009; see the attached pdf files).

In the study conducted by Cardoso et al. (2009), 83 patients with suspected photoaggravated facial dermatitis or systemic dermatitis were tested with a series of potential photoallergens, including isopentyl p-methoxycinnamate (at a concentration of 10%). Only one patient showed a positive reaction to isopentyl p-methoxycinnamate.

In the study of Chew et al. (2010) 50 patients with chronic actinic dermatitis underwent sensitisation and photosensitisation patch tests with 10 suspected photoallergens, among them isopentyl p-methoxycinnamate (used at a concentration of 10% in petrolatum). No positive reactions to isopentyl p-methoxycinnamate were observed in this study.

Pentinga et al. (2009) subjected 18 patients sensitive to cinnamate-related compounds to a photopatch test with 12 cinnamate-like compounds, including isopentyl p-methoxycinnamate (used at a concentration of 10% in petrolatum). None of the study subjects showed a positive reaction to isopentyl p-methoxycinnamate.

The results of these 3 studies in humans suggest that isopentyl p-methoxycinnamate is virtually devoid of any photosensitising activity in humans.

Migrated from Short description of key information:
The skin sensitisation potential of isopentyl p-methoxycinnamate was evaluated in a guinea pig maximisation test in Dunkin-Hartley guinea pigs. The study was performed according to OECD guideline no. 406 and EU method B.6.
In addition, three photopatch tests in humans (Cardoso et al. 2009; Chew et al. 2010; Pentinga et al. 2009; see the attached pdf files) are included in which only one patient in one of the studies showed any signs of photosensitising potential.

Justification for selection of skin sensitisation endpoint:
Guideline study performed in accordance with GLP

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Additional information:

Migrated from Short description of key information:
The respiratory sensitisation potential of isopentyl p-methoxycinnamate was not studied.

Justification for classification or non-classification

According to the results of the guinea pig maximisation test and the 3 studies in humans, isopentyl p-methoxycinnamate does not meet the current EU-CLP criteria for classification as a skin sensitiser. No risk phrase is required.

The respiratory sensitisation potential of isopentyl p-methoxycinnamate was not evaluated. Hence, this substance cannot be classified with respect to this endpoint.