Heptanoic acid

Skin sensitisation

Administrative data

Endpoint:

skin sensitisation: in vivo (non-LLNA)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: 1a. OECD guideline 406 followed under GLP procedures

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1997

Report date:

1997

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 406 (Skin Sensitisation)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.6 (Skin Sensitisation)

Deviations:

no

GLP compliance:

yes

Type of study:

guinea pig maximisation test

Justification for non-LLNA method:

study performed before the implementation of reach regulation.

Test material

Test material information

Constituent 1

Reference substance name:

Heptanoic acid

EC Number:

203-838-7

EC Name:

Heptanoic acid

Cas Number:

111-14-8

Molecular formula:

C7H14O2

IUPAC Name:

heptanoic acid

Details on test material:

- Name of test material (as cited in study report): n-heptanoic acid
- Substance type: carboxylic acid
- Physical state: liquid
- Analytical purity: 99.51 %
- Purity test date: 10 september 1996
- Lot/batch No.: 9604035
- Expiration date of the lot/batch: september 1997
- Storage condition of test material: in dark at room temperature

In vivo test system

Test animals

Species:

guinea pig

Strain:

Dunkin-Hartley

Sex:

male/female

Details on test animals and environmental conditions:

TEST ANIMALS
- Source: Centre d'Elevage Lebeau, 78950 Gambais, France.
- Age at study initiation: approximately three months old
- Weight at study initiation: 323 +/- 13 g for the males and 346 +/- 16 g for the females
- Housing: individually in polycarbonate cages
- Diet : free access to "106 pelleted diet"
- Water : ad libitum
- Acclimation period: at least five days before the beginning of the study


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 21 +/- 2
- Humidity (%): 30 to 70
- Air changes : about 12 cycles/hour of filtered, non-recycled air
- Photoperiod : 12 hrs dark / 12 hrs light


IN-LIFE DATES: From: 21 november 1996 To: 20 december 1996

Study design: in vivo (non-LLNA)

Induction

Route:

intradermal and epicutaneous

Vehicle:

paraffin oil

Concentration / amount:

concentration for induction exposure :
- intradermal injection: n-Heptanoic acid at 1% (w/w) in paraffin oil
- topical application: n-Heptanoic acid undiluted
concentration for challenge exposure:
- topical application: n-Heptanoic acid undiluted

Challenge

Route:

epicutaneous, occlusive

Vehicle:

paraffin oil

Concentration / amount:

concentration for induction exposure :
- intradermal injection: n-Heptanoic acid at 1% (w/w) in paraffin oil
- topical application: n-Heptanoic acid undiluted
concentration for challenge exposure:
- topical application: n-Heptanoic acid undiluted

No. of animals per dose:

- Control group (five males and five females)
- Treated group (ten males and ten females)

Details on study design:

RANGE FINDING TESTS: preliminary tests were conducted on male and female animals in order to determine the concentration to be used in the main study
Preliminary study:
- Administration by intradermal route: Concentrations of 0.1, 1, 5, 10 and 25 % (w/w) were tested. At 5, 10 and 25 % (w/w) necrosis was induced and a slight irritation was induced at 0.1, 1 % (w/w). Concentration chosen for the main study was 1 % (w/w).
-cutaneous route: several concentrations were tested (25 to 100 %) and scoring after 24h and 48h after removal of the dressing. All concentrations were well tolerated systematically and locally by male and female animals. The highest concentration was retained for the two topical application on day 8 and 22 of the definitive test.

MAIN STUDY
A. INDUCTION EXPOSURE
- No. of exposures: 2 (intradermal route on day 1 (3 injections of 0.1ml ) and cutanaous route on day 8)
- Test groups: n-Heptanoic acid in FCA
- Control group: FCA only
- Site: dorsal region between the shoulders
- Duration: day 0 to 8 then day 8 to 22
- Concentrations: intradermal injection 1 % (w/w) and cutaneous application undiluted

B. CHALLENGE EXPOSURE
- No. of exposures: 1
- Day(s) of challenge: day 22
- Exposure period: 24h
- Test groups: n-Heptanoic acid
- Control group: n-Heptanoic acid
- Site: posterior right flank (left flank -vehicule control-)
- Concentrations: undiluted (0.5 ml of the test substance was applied on skin)
- Evaluation: 24 and 48h after challenge

Challenge controls:

no challenge control

Positive control substance(s):

yes

Remarks:

2,4-dinitro Chlorobenzene (DNCB)

Results and discussion

Positive control results:

The sensitivity of the guinea-pigs was checked with a sensitizer: 2,4-Dinitrochlorobenzene (DNCB). During the induction period the reference substance DNCB was applied at the concentration of 0.1% (w/w) (day 1) and 1% (w/w) (day 8). For the challenge application, the DNCB was applied to the right flank at a concentration of 0.5 % (w/w). Under the conditions of this test, DNCB at a concentration of 0.5 % (w/w) induced positive skin sensitization reactions in 50 % of the guinea-pigs.

In vivo (non-LLNA)

Results

Results 1

Reading:

1st reading

Hours after challenge:

24

Group:

negative control

Dose level:

undiluted

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

very slight erythema (grade 1) in 6/10 animals, dryness of the skin in 2/10 animals

Results 2

Reading:

2nd reading

Hours after challenge:

48

Group:

negative control

Dose level:

undiluted

No. with + reactions:

0

Total no. in group:

10

Clinical observations:

very slight erythema (grade 1) persisted in 5/10 animals and dryness of the skin in all animals

Results 3

Reading:

1st reading

Hours after challenge:

24

Group:

test chemical

Dose level:

undiluted

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

very slight erythema (grade 1) in 6/10 animals and dryness of the skin in 8/20 animals.A well-defined erythema (grade 2) was also noted in 1/20 animals.

Results 4

Reading:

2nd reading

Hours after challenge:

48

Group:

test chemical

Dose level:

undiluted

No. with + reactions:

0

Total no. in group:

20

Clinical observations:

very slight erythema (grade 1) in 5/5 animals and dryness of the skin in all animals. Crusts were observed in 1/20 animals.

Results 5

Reading:

other:

Group:

positive control

Remarks on result:

other: DNB induced positive reactions in 50% of animals.

Applicant's summary and conclusion

Interpretation of results:

not sensitising

Remarks:

Migrated information

Conclusions:

According to the maximization method of Magnusson and Kligman, no cutaneous reactions attributable to the sensitization potential of the test substance n-Heptanoic acid (batch No. 9604035) were observed . Classification: not sensitizing according to EU and GHS classification.

Executive summary:

In a skin sensitization test (CIT, 1997), the potential of n-Heptanoic acid (batch No. 9604035) to induce delayed contact hypersensitivity was evaluated in guinea pigs according to the maximization method of Magnusson and Kligman OECD 406. Thirty animals were allocated to 2 groups: a control group 1 (5 males/ 5 females) and a treated group 2 (10 males/ 10 females). Skin reactions were evaluated approximatively 24 and 48h after removal of the dressing. At the end of the study animals were killed without examination of internal organs (no necropsy). Skin samples were taken from the posterior left and right flanks of all animals and were preserved in 10 % buffered formalin.

No clinical signs and no deaths were observedduring the study. The body weight gain of the treated animals was normal when compared to that of the control animals.

On day 10, after the cutaneous application of the induction period, signs of irritation were observed at the test site (dorsal region between shoulders) in the control and treated groups. After the cutaneous challenge application, at the 24-hour reading, slight cutaneous reactions (very slight erythema in 6/10 animals, dryness of the skin in 2/10 animals) were noted in the control group. These reactions persisted at the 48-hour reading (very slight erythema in 5/10 animals and dryness of the skin in all animals).

In the treated group, the same cutaneous reactions were observed: very slight erythema in 6/20 animals at the 24-hour reading and in 5/20 animals at the 48-hour reading, dryness of the skin in 8/20 animals at the 24-hour reading and in all animals at the 48-hour reading. A well-defined erythema was also noted in 1/20 animals at the 24-hour reading and crusts were observed in 1/20 animals at the 48-hour reading. After the microscopic examination, the cutaneous reactions observed in both groups were attributed to slight irritant properties of the test substance. The sensitivity of the guinea-pigs was satisfactory since 50% of the animals showed a positive reaction with DNCB.

Under the tested condition and according to the maximization method of Magnusson and Kligman, the test substance n-Heptanoic acid does not induce delayed contact hypersensitivity in guinea-pigs.