Sulphanilic acid

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

In a reliable study (acc. to OECD test guideline 429), which was assigned as key study, the test substance suspended in propylene glycol was assessed for its possible contact allergenic potential. For this purpose a local lymph node assay was performed using test item concentrations of 5, 10, and 25%. The animals did not show any clinical signs during the course of the study and no cases of mortality were observed. A test item is regarded as a sensitiser in the LLNA if the exposure to one or more test concentration resulted in 3-fold or greater increase in incorporation of 3HTdR compared with concurrent controls, as indicated by the Stimulation Index (S.I.). The estimated concentration of test item required to produce a S.I. of 3 is referred to as the EC3 value. In this study Stimulation Indices (S.I.) of 0.84, 0.98, and 0.79 were determined with the test item at concentrations of 5, 10, and 25% in propylene glycol, respectively. The test substance was not a skin sensitiser in this assay.

As sulfanilic acid is legally classified as a skin sensitiser (according to Regulation (EC) No 1272/2008), further evidence is provided.

In the study of Basketter et al. (1992), data on sulphanilic acid derived from the GPMT has been compared with results from a second guinea pig assay (the cumulative contact enhancement test) and the murine local lymph node assay, both of which require only topical application of chemical. Except for the GPMT, no test identified any sensitizing activity associated with exposure to sulphanilic acid. These latter results are consistent with the experience gained from substantial human exposure in an occupational setting and from which no cases of allergic contact dermatitis to sulphanilic acid have arisen over a 20-year period.

As the GMPT intradermally injects the substance, its relevance is questioned in the light of the available human evidence, showing no potential of skin sensitisation.

Furthermore, data from an in chimico test method, which is currently being pre-validated by the European Commission, are available:

One unifying characteristic of chemical allergens is the requirement that they react with proteins for the effective induction of skin sensitization. The majority of chemical allergens are electrophilic and react with nucleophilic amino acids. To determine whether and to what extent reactivity correlates with skin sensitization potential, 82 chemicals comprising allergens of different potencies and nonallergenic chemicals were evaluated for their ability to react with reduced glutathione (GSH) or with two synthetic peptides containing either a single cysteine or lysine. Following a 15-min reaction time with GSH, or a 24-h reaction time with the two synthetic peptides, the samples were analyzed by high-performance liquid chromatography. UV detection was used to monitor the depletion of GSH or the peptides. The peptide reactivity data were compared with existing local lymph node assay data using recursive partitioning methodology to build a classification tree that allowed a ranking of reactivity as minimal, low, moderate, and high. Generally, nonallergens and weak allergens demonstrated minimal to low peptide reactivity, whereas moderate to extremely potent allergens displayed moderate to high peptide reactivity. Classifying minimal reactivity as nonsensitizers and low, moderate, and high reactivity as sensitizers, it was determined that a model based on cysteine and lysine gave a prediction accuracy of 89%. The results of these investigations reveal that measurement of peptide reactivity has considerable potential utility as a screening approach for skin sensitization testing, and thereby for reducing reliance on animal-based test methods.

Sulphanilic acid did not deplete the representative proteins and has been classified as a non-sensitiser.

Taking this data together, sulfanilic acid is considered not to be as a skin sensitiser.

Migrated from Short description of key information:
Based on a reliable LLNA-Study (key) and supportive evidence from further non-invasive in vivo tests and in chimico test (currently undergoing prevalidation), sulfanilic acid is considered not to be skin sensitising.

Justification for classification or non-classification

Based on the available evidence, sulfanilic acid is considered to be not a skin sensitiser. Therefore, no classification is warranted.