Q: "My 13-year-old daughter wants to dye her hair, but I've told her she can't as I think she's too young to use hair dye and I'm worried she might have an allergic reaction to it. She thinks I'm over-reacting – am I?"
A: Consultant dermatologist Dr David Orton, of the British Association of Dermatologists, says: "Allergies can have an enormous impact on people's lives and as such it's important to be aware of this potential hazard.
"The chemicals used in permanent oxidative hair dyes are well recognised as sensitisers, having the capacity to cause allergic reactions. The younger someone starts to regularly use such products, the more will be their lifetime risk of developing contact allergy to its chemical constituents.
"Manufacturers of these cosmetics are well aware of their potential to cause severe allergic reactions, which is why they voluntarily print such warnings on the packaging.
"A recent study has shown that over the last 10 years there has been an increase in child allergies to p-Phenylenediamine (PPD), an ingredient in hair dyes, probably linked to more young people using them. The numbers with a contact allergy to PPD in one patch testing clinic went from 8 per cent of the children they tested to 16 per cent.
"Another important related risk is the trend for young people to have black henna tattoos. Black henna (as opposed to plain henna) often has extremely high and unregulated concentration of PPD added to the henna, and having such a tattoo can greatly increase your risk of becoming allergic to PPD and therefore subsequently reacting to oxidative hair dyes.
"Finally, it's worth knowing that an allergy to hair-dye chemicals can sometimes put people at risk of developing cross-reactions to other chemicals unrelated to hair dyes such as topical local anaesthetics."