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What happens when your client develops a reaction to hair colour?

It can be a salon’s worst case scenario. You’ve coloured a client’s hair and they’ve come back to you showing a reaction on their scalp or face. If you’re alert and sufficiently knowledgeable to identify that the reaction is an allergic one, and not a temporary irritation, one of the most important pieces of advice you can give your client is to go and see their GP to get medical advice.

Getting an appointment to see a GP may be easier said than done. But once there the GP will want to know exactly what’s happened, when and whether it’s happened before. After taking a close look at the situation, the GP may recommend the client sees a consultant dermatologist – a skin specialist – so the issue can be examined and explored more thoroughly.

John English is a consultant dermatologist in Nottingham. Like many of his colleagues, he’s seeing a considerable increase in the number of people coming to see him with evidence of allergy to cosmetics products. “It’s not just hair dye that’s the culprit”, he says, “the biggest increase we’re seeing is sensitivity to a common preservative that’s found in many leave-on and wash-off products called metathylisothiazolinone.”

A dermatologist will test their patient for allergy is by using a diagnostic patch test. This involves placing an adhesive strip or strips on the skin, usually on their upper back. The strip contains a number of small, shallow containers or ‘chambers’. These can be filled with different substances that test for allergy or sensitivity to different products or allergens.

An allergen is a substance that causes allergy or sensitivity in an individual. Some allergens are found in foods like nuts and seafish, others are found in man-made chemicals and products. Different people will react to allergens in different ways, and some people may react severely to an allergen that causes no response in others.

The dermatologist might choose to test for just one or two allergens or a number at the same time, depending on the patient’s history. But however many they’re testing for, they’ll keep a careful note of what’s been tested and on which patch of skin.

The strip is left on the skin for at least 24 hours, and the patient is told not to wash the area during that time. The dermatologist will then remove the strip and examine the skin. If there’s been a reaction, the skin is likely to be raised and red. Often the dermatologist will use a special reference chart to measure whether there’s been a reaction and how severe it is.

“I recently saw a patient who’d had a severe reaction to colour, on both their hair and eyebrows,” says John English, “I tested for 55 substances at the same time and she tested positive for 3: bleach, ammonium sulphate and PPD, which is the most active substance in dark hair colour.”

Following that result, what was John English’s advice to the patient? Some of his colleagues will advise a patient never to use hair colour again in this situation. But he takes a more pragmatic view. “I think we have to acknowledge that colour not going away. My view is that unless the case is very severe, colour can still be used provided the hairdresser is very careful, and the colour does not touch the surface of the skin.”

It’s a Catch-22 situation. Because hair colour can be dangerous for some people, a skin test should always be used before applying colour. But the test itself contains small amounts of the very substance that can cause a problem. So what’s to be done?

“In an ideal world”, says John English, “we would ban all PPD-based hair colour, but that’s not going to happen. The message has to be: be very careful, don’t overuse colour and test every time.”