Registration Dossier

Administrative data

health surveillance data
Type of information:
experimental study
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: This study is well described but presents criticable points, which should be taken into account for the interpretation. Those points are quoted in the Conclusion (CL) freetext.
Reason / purpose for cross-reference:
reference to same study

Data source

Reference Type:
A comparison of rabbits and human skin response to certain irritants.
Phillips L, Steinberg M, Maibach HI and Akers WA.
Bibliographic source:
Toxicology and Applied Pharmacology, 21 : 369-382.

Materials and methods

Study type:
human medical data
Test guideline
no guideline followed
GLP compliance:

Test material

Constituent 1
Chemical structure
Reference substance name:
Undec-10-enoic acid
EC Number:
EC Name:
Undec-10-enoic acid
Cas Number:
Molecular formula:
undec-10-enoic acid
Details on test material:
Source: no data
Batch number: no data
Purity: no data


Type of population:
Details on study design:
Several irritation test were performed on humans. 1 - Draize-like irritation test achieved on 16 adult white men. Their both forearms were clipped 24h prior testing. 0.5 ml of a 30%(w/v) of uncecylenic acid in ethanol solution was applied and covered with gauze patch for 24h. Results were assessed according Draize's score 30 minutes after removal of the patch. 2 - 21-day continuous closed patch test 12 adults were divided in 4 groups of 2 each. Each group was tested with one of the following concentrations: 1%, 10%, 20% and 40%. Patches, covering 0.2 ml of tested solution,were placed in a paraspinal location on each subject's back for 24h. Results were scored 30 min after patch removal according to the following scale: No sign or questionable erythema: 0 Definite erythema of the entire patch area: 1 Erythema and induration: 2 Vesiculation: 3 Bullous reaction: 4 Testing was continued daily for 21 days or until grade 4 reaction was obtained. Cumulative irritation index is the addition of previous daily scores all along the 21 days. 3 - 21-day open testing 7 men received 0.02 ml of undecylenic acid solution at different concentrations (10%, 20%, 40% and 60%) in a paraspinal area (2 men per concentration, except for 40%). This area was delimited by a petrolatum ring, allowing to confine the test liquid. Evaluation schedule and scale were the same as previous ones.

Results and discussion

See below

Any other information on results incl. tables

1 - Draize-like test yield no irritation. Actually, irritation index was  zero.

2 - 21-days continuous closed patch test
Cumulative irritation index (CII) at 21 days for the different concentrations are described below:

Concentration CII
1% 0.0
10% 38.5
20% 50.5
40% 69.0

3 - 21-day open testing
Whatever concentration (up to 60%), cumulative irritation index remained equal to zero.

Applicant's summary and conclusion

Undecylenic acid are tested in different conditions on healthy male volunteers.
The Draize-like irritation test does not yield any skin toxicity after a 24h exposure of a 30% (w/v) solution.
However, a 21-day exposure reveals a dose related irritation. This irritation seems to be time-dependant even if no data are available in terms of time. Previous test suggests that no symptom is visible after a 24h exposure, even if the studied area is different (back versus forearm).
Attention should be drawn to the lenght of exposition, which could hedge the results because of sensitisation phenomenon.
The 21-day open test does not highlight any irritation.
However, il is difficult to ascribe this harmlessness to the patch since the applied volume was 10-fold lower (0.02 ml versus 0.2 ml).
Nevertheless, this study provides useful data on human exposure and allows to consider undecylenic acid as a slight irritant.