BACKGROUND: Toluene-2,5-diamine (PTD) is the most frequently used dye in oxidative hair dyes on the Scandinavian market. However, little is known about immune responses to PTD-containing oxidative hair dyes.

OBJECTIVES: To study immune responses induced by PTD-containing hair dyes in mice.

METHODS: Immune responses against two different permanent hair dye products containing 1·60% (w/w) and 0·48% (w/w) PTD within the colour gel, and various concentrations of pure PTD were studied. The local inflammatory response was measured by ear swelling and cell infiltration, and T- and B-cell infiltration and proliferation was determined in the draining lymph nodes.

RESULTS: Concentration-dependent immune responses were seen to PTD both in the skin and draining lymph nodes. The hair dye containing 1·60% PTD induced strong local inflammation and caused T- and B-cell infiltration and proliferation as well as an increased number of regulatory T cells in the draining lymph nodes. In contrast, the hair dye containing 0·48% PTD induced skin inflammation but only minor responses in the draining lymph nodes.

CONCLUSIONS: Consumer-available PTD-containing permanent hair dyes can be potent immune activators inducing both pro- and anti-inflammatory responses. The outcome of the response is dependent on allergen dose, amount of additional allergens and exposure regime.