L-methionine

Endpoint summary

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

No skin sensitization study is available for L-methionine.

Skin sensitization is the process following the epicutaneous application of a substance to the skin which results in an immunological response specific for this substance. Skin sensitisation is also called "delayed contact hypersensitivity", "contact hypersensitivity", "contact allergy" or "allergic contact dermatitis". To behave as a contact allergen, a substance must penetrate into the skin and react with proteins. L-methionine is a normal constituent in living cells occurring as a free amino acid, bound to RNA and incorporated in proteins and peptides. Therefore, it is highly improbable that L-methionine acts as a skin sensitizing agent. Further, L-methionine is used in parenteral nutrition, as a dietary supplement, in biochemical research, in cell culture media, as a feed additive, and is a component found in skin cosmetics. Based on the available information, there is no human or animal data that indicates L-methionine to be a skin sensitizer. Considering the extensive, widespread dermal exposure to L-methionine the absence of case reports of humans showing skin reactions is consistent with L-methionine having a very low /no skin sensitization potential.

 

The dermal sensitization of D,L-methionine was investigated with guinea pigs in a GLP study according to OECD guideline 406 (2002 -0520 -DGT). D,L-Methionine revealed no sensitizing properties in guinea-pigs in this skin sensitization test according to the Buehler method.Read-across of the D,L-methionine study to L-methionine can be applied due to structural and physico-chemical similarities according to Reach regulation (Annex XI, 1.5). Further, L-methionine is present in a considerable amount in racemic methionine (approximatly 50%). The remaining 50% (D-methionine) contain the same set of functional groups and is not believed to have specific activity (e.g. chemical reactivity, differences in skin penetration properties, cell damaging/irritating properties) relevant for skin sensitization. Taking this into account it can be concluded that D,L-methionine has the same properties regarding skin sensitization as L-methionine. Therefore, based on the results of the read-across substance D,L-methionine, L-methionine can be regarded/classified as not skin sensitizing.

This is supported by an EFSA publication (EFSA Journal 2013;11(10):3428) which summarizes an available OECD 406 study with L-methionine. Twenty Hartley guinea pigs were treated dermally with a 45 % suspension of L-methionine in olive oil (0.5 mL/site) and challenged two weeks later either with the vehicle or with 45 % L-methionine (Buehler method). There was no evidence of a response after the challenge, therefore L-methionine can be regarded as not skin sensitizing. However, the full study report is not available to the registrant.

Migrated from Short description of key information:
L-Methionine is not a skin sensitizer.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed (not sensitising)

Additional information:

From experience L-methionine is not sensitizing via the respiratory route. Studies on this endpoint are not available.

Migrated from Short description of key information:
From experience of the handling of L-methionine in industrial and commercial surroundings, L-methionine is not sensitising via the respiratory route.

Justification for classification or non-classification

L-Methionine is considered as not sensitising and does not trigger respective classification.