A mixture of isomers of: 1,1'-[(3,5(or 2,4 or 4,6 or 2,6)-dihydroxy-o(or m or p)-phenylene)bis(azo-meta-phenyleneazo{1-[3-(dimethylamino)propyl]-1,2-dihydro-6-hydroxy-4-methyl-2-oxopyridine-5,3-diyl})]dipyridinium-dichloride-dihydrochloride; 1-(1-[3-(dimethylamino)propyl]-5-{3-[x-(4-{1-[3-(dimethylamino)propyl]-1,6-dihydro-2-hydroxy-4-methyl-6-oxo-5-pyridinio-3-pyridylazo}phenylazo)-2,4(or 2,6 or 3,5 or 4,6)-dihydroxyphenylazo]phenylazo}-1,2-dihydro-6-hydroxy-4-methyl-2-oxo-3-pyridyl)pyridinium-dichloride-dihydrochloride (where x is variable)

Endpoint summary

Description of key information

Skin sensitising.

Key value for chemical safety assessment

Skin sensitisation

Endpoint conclusion

Endpoint conclusion:

adverse effect observed (sensitising)

Additional information:

Guinea pig maximization test

A study was run according to OECD guideline 406 to assess the potential of test substance to induce delayed contact hypersensitivity (skin sensitisation) in the guinea pig. The substance resulted in a sensitization rate of 100 per cent after intradermal induction with 0.5 % test item solution and epicutaneous challenge application of the test item of 25 % to the guinea pig. According to the results, the substance is considered to be sensitising in this test.

Buehler test

A study was run following OECD guideline 406, to assess the skin sensitising potential of test substance in guinea pig. The substance gave no sign of skin sensitisation, indeed 0/20 positive responses were found upon 3 inductions at 25 % in physiological saline (one application per week, occlusive application for 6 h each time) and a challenge at 25 % (2 weeks after the last induction, occlusive application for 6 h, gradings at 24 and 48 h after challenge). The negative control gave 0/10 positive responses. Consequently, the test substance was considered as devoid of a skin sensitising potential in this assay.

Respiratory sensitisation

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

Two studies were availble, a GPMT and a Buehler test. Despite the test material was the same, conflicting evidences were found.

Experimental findings in the GPMT would imply a classification as skin sensitizer category 1A according to the CLP Regulation (EC 1272/2008), while experimental results in the Buehler assay would imply no classification.

However, the substance is listed in Annex VI of the CLP Regulation (EC 1272/2008), with index no. 611-016-00-8 and classification as Skin Sens. 1, H317.