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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

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:

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.