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Description of key information

Key value for chemical safety assessment

Skin sensitisation

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

There is no information on sensitisation in humans after exposure to trimethylbenzenes.

In animals a key study is provided by Shell Toxicology Laboratory (1977). Guinea pigs were challenged with Shellsol A (a mixture of trimethylbenzenes CAS No 64742 -95 -6) in a maximization test. No sensitisation response was elicited immediately, 24 or 48 hours after the challenge. The test was therefore negative. This result is supported by a poorly reported guinea pig maximization test (IUCLID 4 record; EBSI, 1983) where no sensitisation occurred after exposure to 1,2,4-trimethylbenzene (study unavailable).

In contrast, dermal responses were reported when Aromasol H (a mixture of C8 aromatics (xylenes and benzenes), C9 aromatics (trimethylbenzenes and ethyl toluenes), and C10 aromatics (diethyl ethyl benzenes and diethyl benzenes) was tested in a guinea pig maximization test (CTL1984). The study report concluded that Aromasol H was a weak sensitizer but irritation was also noted. Irritation has been reported to be a factor in false positive results obtained on other substances in the guinea pig maximization test (Basketter, 2008). The substituted aromatics present in Aromasol H are known to be non-sensitising, hence the weight of evidence therefore indicates that this result is a false positive.

In conclusion, the available evidence indicates that 1,2,4-trimethylbenzeneis not a skin sensitiser.


Basketter D (2008). Information derived from sensitization test methods: Test sensitivity, false positives, and false negatives. Reg. Tox. Pharm. 50, 68–169.

Migrated from Short description of key information:
A weight of evidence evaluation indicates that of 1,2,4- trimethylbenzene is not-sensitising. Two guinea pig maximization tests with mixtures containing trimethylbenzenes were negative. One study gave a positive result but this is believed to be a false positive due to irritation.

Justification for classification or non-classification

1,2,4-Trimethylbenzene is not considered to be sensitizing. It does not therefore warrant classification under DSD or CLP.