Permanent hair dyes contain ingredients which can cause allergies. Symptoms range from a burning sensation and redness or rash, to weeping blisters, chemical burns and severe swelling of the face. Anaphylactic shock is rare but it happens. The allergic reaction can occur at any time – from the first time you use dye or suddenly after many years of trouble-free use. Alarmingly, these same allergens can be found in some henna hair products and henna tattoos - not quite where you'd expect them.
Allergens - what to look for
The main culprits are p-phenylenediamine (PPD), Toluene-2,5-diamine (TD) and Toluene-2,5-diamine sulphate (TDS). These are the ingredients that make the dye permanent when oxidised with hydrogen peroxide.
PPD appears to have the strongest allergenic potential, followed by TD then TDS . PPD is found in most permanent dye products on the market, and it's also found in some henna products for hair and temporary tattoos. Getting a temporary tattoo may sensitise you to future contact (more below).
PPD used to be banned from hair dyes in some European countries, but it's now considered okay if it comprises less than six percent of a product. Manufacturers aren't required to state exactly how much PPD is present and, depending on the colour, the level can vary. There tends to be more PPD in darker dyes. There are some products, such as Herbatint, which contain lesser amounts of PPD than other products, and this may help reduce the risk of developing an allergy.
Skin patch test for allergies
Products with these sensitisers carry warnings and recommend you do a skin sensitivity (patch) test, where a small amount of dye is applied to your forearm or behind the ear. If there is no reaction within 48 hours, it’s presumed you are safe to use it.
However, the EU Scientific Committee on Consumer Products points out that this is no guarantee: there are many misleading and false-negative results, and it can take up to a week to react to the allergen, not 48 hours. They also point out the patch test can actively sensitise people to the allergen, so when they apply the dye to their hair two days later they get an allergic reaction .
While most people are likely to never develop a hair dye allergy, you can reduce the risk by making sure not to get the dye on your skin, using gloves to apply the dye and making sure you don’t leave the dye on longer than the recommended time.
Your options if you’re allergic
• If you’re allergic to PPD, you may also be allergic to TD and TDS, because they’re similar chemicals. However, studies have found that it’s possible to be allergic to one but not others. If you have a confirmed allergy to one, it could be worth trying a hair colour with the other – but do two patch tests a week apart, and only apply colour to hair a week after a clear second patch test. If you’ve suffered a severe reaction in the past, try this only after consulting your dermatologist.
• Hydroxyethyl-p-phenylenediamine sulfate, another known sensitiser similar to PPD, has also recently been tested on people with PPD allergies – some reacted, but most did not . It’s not yet used in products available in Australia, but may provide an alternative to PPD in future products.
• For mild allergies, ask the hairdresser for foils and specify that the dye doesn’t touch your scalp, or stick with highlights using a cap.
• You could try henna products, including those mixed with indigo for a brown rather than red effect. Senna gives a golden tint to grey or blonde hair. Some plant dye products contain PPD (see below) or metallic salts, so check ingredients.
• Beware many products that suggest they’re natural or organic still contain these chemicals.
• If you’re allergic to hair dye, you may also be allergic to benzocaine, a topical anaesthetic used in some anti-itch creams, dental and medical ointments and cough drops.
PPD in henna
These and some other henna products – especially black or dark henna – contain PPD, and are therefore unsuitable for people with hair dye allergies. If you’re buying henna products because of allergies to conventional hair dyes, check the ingredients carefully.
Henna tattoos – steer clear
That ‘temporary’ black henna tattoo you or the kids get on holidays may become a lasting souvenir. The girls in this picture got black henna tattoos while on holiday in Egypt, and a few days later blistered in perfect synchrony with the original tattoos.
Paraphenylenediamine (PPD) is often used in henna to make it darker and to dry faster, and similar allergic reactions have been reported among Australians holidaying in Asia. They’ll never be able to use hair dye containing PPD, and are also potentially allergic to para-aminobenzoic acid (PABA – found in some sunscreens), benzocaine and sulfonamides (a class of medicines which includes some antibiotics, diuretics and anticonvulsants).
Almeida PJ & Borrego L. Snapshot: Temporary henna tattoos with long-term consequences. MJA 2009; 191 (11/12): 687. © Copyright 2009 Medical Journal of Australia – reproduced with permission.