Registration Dossier

Administrative data

Description of key information

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not sensitising)
Additional information:

No test results for L-leucine are available. However, read-across to the test results available for structural analogue L-valine is deemed justified based on a comparison of the main factors driving skin sensitisation: the chemical reactivity (functional groups) of the substance and its tendency to undergo dermal absorption, which in itself is determined by the substance's molecular weight, log Kow and water solubility.

- both are essential amino acids that are in the zwitterion state at physiological pH

- the chemical structure differs only in that L-leucine has one extra methylene group in the aliphatic side chain

- both amino acids are quite small molecules with a low MW (LEU: 131 g/mol, VAL: 117 g/mol), which favors dermal uptake, however

- both amino acids have log Kow values below -1 (LEU: -1.52, VAL: -2.26) which suggests that these substances are most likely not sufficiently lipophilic to cross the stratum corneum

- the water solubility of leucine and valine is high (LEU: 23 g/L, VAL: 58 g/L). In combination with a low log Kow, it can be assumed that these substances will be too hydrophilic to cross the lipid rich environment of the stratum corneum. As a consequence, dermal uptake will be low.

As the chemical reactivity and the dermal uptake of L-leucine and L-valine are almost identical, it can be concluded that read-across of skin sensitisation information between those 2 substances is acceptable.

The tests available for L-valine are carried out according to OECD guidelines and reveal no effects of skin sensitisation. L-valine was concluded to not be sensitising to the skin. As a consequence, skin sensitisation effects are not expected to occur upon exposure to L-leucine.


Migrated from Short description of key information:
No test results for L-leucine are available. However, based on test results available for read-across substance L-valine it can be concluded that skin sensitisation is not expected upon exposure to L-leucine.

Justification for classification or non-classification

In accordance to Directive 67/548/EEC (Dangerous Substances Directive), classification is not necessary for skin sensitisation based on the available test data for read-across substance L-valine.

In accordance to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008, classification is not necessary for skin sensitisation based on the available test data for read-across substance L-valine.