Piperonal

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

February 1977

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1977

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Testing methods:
I. Single application: 0.025 ml of undiluted compound and of its progressively diluted solutions to an area measuring 2 square centimetre of 6 to 8 animals per group. After evaporation of the solvent, the application site was left uncovered. The reactions were recorded after 24 hours application, and then the dose-response curve was established.

II. 21 day repeated application test: This test is aimed to determinate the tolerance threshold on guinea pig, which can be used in further sensitisation test (open epicutaneous test). 0.1 ml of undiluted compound and of its progressively diluted solutions were applied to an area measuring 8 square centimetre on the clipped flank skin of 6 to 8 guinea pigs per concentration group, using 4 to 6 such groups for each compound. The applications were repeated daily for 21 days at the same skin site. The application site was left uncovered and the reactions were recorded 24 hours after each application. For the challenge procedure, all of the guinea pigs previously treated for 21 days were tested on Days 21 and 35 on the contralateral flank with the same compound at the minimal irritating concentration and at some lower non-irritant concentrations.

GLP compliance:

no

Remarks:

(Study pre-dates GLP requirements)

Test material

Test material information

Constituent 1

Reference substance name:

Piperonal

EC Number:

204-409-7

EC Name:

Piperonal

Cas Number:

120-57-0

Molecular formula:

C8H6O3

IUPAC Name:

1,3-benzodioxole-5-carbaldehyde

Test material form:

not specified

Details on test material:

-Name of the test material as cited in the publication: Heliotropin

Test animals

Species:

guinea pig

Strain:

other: Himalayan white-spotted guinea pigs

Details on test animals or test system and environmental conditions:

The animals were male and female bred at the Institute of Biomedical Research, Fullinsdorf, Switzerland. The guinea pigs weighed 400 to 500 g. They were fed on pelleted feed supplemented with green vegetables, carrots and vitamin C in the drinking water, all available ad libitum.

Test system

Type of coverage:

open

Preparation of test site:

clipped

Vehicle:

other: not specified: acetone, ethanol, diethyl phthalate, water, polyethylene glycol, or vaseline

Controls:

yes

Amount / concentration applied:

Concentration: Undiluted and 30, 10, 3, 1, 0.3, 0.1, 0.03% (or less when necessary)
Amount applied: 0.1 mL (induction) and 0.025 mL (challenge)

Duration of treatment / exposure:

I. Single application

II. Once per day, repeated for 21 days (induction), then on Days 21 and 35

Observation period:

I. 24 hours after application

II. Every 24 hours after each application

Number of animals:

I. 6 to 8 animals per group (no detailed information for each test substance)

II. 6 to 8 animals per group; 4 to 6 such groups for each compound (no detailed information for heliotropin)

Details on study design:

I. Single application: 0.025 ml of undiluted compound and of its progressively diluted solutions to an area measuring 2 square centimetres of 6 to 8 animals per group. After evaporation of the solvent, the application site was left uncovered. The reactions were recorded after 24 hours application, and then the dose-response curve was established. The reactions were read after 24 hours using an "all or none" criterion, i.e., the dose-response curve was established by results. The minimal irritating concentration was defined as the lowest concentration causing mild erythema in at least 25% of animals of the group concerned, and the maximal non-irritant concentration as the highest concentration causing no macroscopically discernible reactions in any of the animals of the group.

II. 21 day repeated application test: This test is aimed to determinate the tolerance threshold on guinea pig, which can be used in further sensitisation test (OET). 0.1 ml of undiluted compound and of its progressively diluted solutions were applied to an area measuring 8 square centimetre on the clipped flank skin of 6 to 8 guinea pigs per concentration group, using 4 to 6 such groups for each compound. The applications were repeated daily for 21 days at same skin site. The reactions were recorded 24 hour after each application. The maximum non-irritant and the minimal irritating concentrations were determined by the “all or none’ criterion. When necrotic or ulcerating reactions were provoked, the application site was changed.

Generally speaking, the degree of the topically irritant effect after one single or after repeated application is characterized by the intensity of the skin reaction and by the magnitude of the minimal irritating concentration. For evaluation of the irritations, we applied the following scale:

0 = no skin reaction
0.5 = red spots
1 = confluent redness
2 = redness plus swelling
3 = redness, swelling, crusts
4 = necrotic skin alteration

For the challenge procedure, all of the guinea pigs previously treated for 21 days were tested on Days 21 and 35 on the contralateral flank with the same compound at the minimal irritating concentration and at some lower non-irritant concentrations. The minimal irritating concentration of each compound was used in order to confirm the biological activity determined after the first application and to exclude false results. These tests were performed by applying with a pipette 0.025 mL of each concentration to skin areas measuring 2 square centimetres. The reactions were read after 24, 48, and/or 72 hours. Based on this procedure, the minimal sensitizing concentration necessary to induce contact hypersensitivity and the minimal eliciting concentration necessary to cause a positive reaction was determined. A concentration was considered allergenic when at least 2 out of 8 animals of the concentration group concerned showed positive reactions with non-irritant concentrations used for challenge, based on practical experience.

Results and discussion

In vivo

Results

Remarks on result:

other: Quantitative data not provided.

Irritant / corrosive response data:

The results show that the substance heliotropin can cause slight irritation to the skin of guinea pigs. However, due to restrictions of reliability of this study, a conclusion cannot be drawn from this study alone.

Other effects:

Information not reported.

Any other information on results incl. tables

During the induction phase, the highest non-irritant concentration for a single application was 3%. After 21 days of daily administration, very slight irritation (3% concentration) or slight irritation (10, 30, and 60% concentrations) was noted. Details were not provided on how many animals at each dose level exhibited the findings or on what constituted a determination of “very slight” or “slight” irritation.

Applicant's summary and conclusion

Interpretation of results:

other: with no quantitative data, interpretation of results is not possible.

Remarks:

Criteria used for interpretation of results: expert judgment

Executive summary:

During the induction phase of an allergenicity study in guinea pigs, the highest non-irritant concentration for a single application of piperonal was 3%. After 21 days of daily administration, very slight irritation (3% concentration) or slight irritation (10, 30, and 60% concentrations) was noted. Details were not provided on how many animals at each dose level exhibited the findings or on what constituted a determination of “very slight” or “slight” irritation. Therefore, the study is considered to be reliable but with restrictions.