Fatty acids, C18-22

Direct observations: clinical cases, poisoning incidents and other

Administrative data

Endpoint:

direct observations: clinical cases, poisoning incidents and other

Type of information:

migrated information: read-across based on grouping of substances (category approach)

Adequacy of study:

weight of evidence

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Acceptable, well documented publication which meets basic scientific principles.

Data source

Reference

Reference Type:

publication

Title:

Relative irritancy of free fatty acids of different chain length

Author:

Stillman, M.A. et al.

Year:

1975

Bibliographic source:

Contact Dermatitis 1:65 - 69

Materials and methods

Study type:

study with volunteers

Endpoint addressed:

skin irritation / corrosion

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

Stearic acid and further fatty acids in 1 M concentrations were applied daily under occlusive patch tests to human skin until detectable erythema appeared or until the experiment terminated after 10 consecutive days of applications. In addition intradermal injections of stearic acid in 0.01 M and 0.1 M concentrations were performed; each site was evaluated at 24 h and 48 h for erythema and induration.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Stearic acid

EC Number:

200-313-4

EC Name:

Stearic acid

Cas Number:

57-11-4

Molecular formula:

C18H36O2

IUPAC Name:

stearic acid

Details on test material:

- Name of test material (as cited in study report): Octadecanoic acid (stearic)
- Analytical purity: no data

Method

Type of population:

general

Subjects:

- Number of subjects exposed: 35 in total: 10 volunteers for patch test (for 1.0 M fatty acids) and 15 volunteers for intradermal injections (5 volunteers for 0.01 M fatty acids and 10 volunteers for 0.01 M and 0.1 M of each fatty acid)).
- Demographic information: white men, not further specified

Route of exposure:

other: dermal (occlusive) and intradermal

Reason of exposure:

intentional

Exposure assessment:

not specified

Details on exposure:

The irritant potential of the test substance in human volunteers was evaluated after (A) dermal and (B) intradermal exposure.

A) For the dermal route, A1-test ® patches (Imeco, Astra Agency, Stockholm, Sweden) were saturated with 0.04 mL test solution (1 M stearic acid in propanol) and applied on the interscapular area of the volunteers. The patch was held in place via occlusive coverage with a Blenderm® tape (Minnesota Mining and Manufacturing Company, St. Paul, MN, USA). After 24 h, the patches were removed and the skin reactions were evaluated 30 min later. If no erythema were visible, the volunteers were re-exposed for a maximum of 10 consecutive days. If erythema were present over the entire patch area, no further application occurred on the respective volunteer and the number of days needed to induce the erythema was recorded. Propanol saturated patches served as vehicle control and were applied to each volunteer.

B) For the intradermal route, 0.1 mL of the test solution (0.01 M and 0.1 M stearic acid in olive oil) were injected into the back of the volunteers. After 24 h and 48 h, each site was evaluated for erythema and induration. As vehicle control, olive oil was injected in all volunteers.

Examinations:

A) Dermal application:
After 24 h exposure, the patches were removed and the skin reactions (erythema) were evaluated 30 min later.

B) Intradermal exposure:
24 h and 48 h after intradermal exposure, each site was evaluated for erythema and induration.

Results and discussion

Clinical signs:

A) Dermal application
1 M stearic acid did not result in the formation of erythema in any of the volunteers within 10 consecutive days of applications.

B) Intradermal injection
All volunteers showed slight indurations of 5 mm and mild erythema after injection of stearic acid (0.01 M and 0.1 M) and the vehicle control (olive oil). No difference between the test and control sites was visible.

Applicant's summary and conclusion

Conclusions:

Under the applied test conditions, stearic acid did not show any skin irritation potential. Daily dermal application of 1 M stearic acid (28.4% (w/v)) did not cause irritation till the termination of the study on day 10 and no differences between control and test sites have been noted after intradermal injections of 0.01 M or 0.1 M stearic acid.