Colour Me Allergic

Hair dyes and temporary dark henna tattoos may cause allergic reactions.  Para-phenylenediamine (PPD) is a preferred component of hair dyes and black henna tattoos due to the long lasting, natural black pigmentation that it imparts.  The base PPD is colourless but develops as a dark dye when oxidised.  During oxidation, partially oxidised PPD is produced and it is this chemical that causes allergy.

PPD allergy appears to be on the rise.  The popularity of temporary dark henna tattoos with children and adolescence has resulted in earlier development of this allergy.  Data shows that there is a 2.5% risk of developing a PPD allergy per tattoo application.  Hairdressers are at risk of developing PPD allergy and must be aware of preventative measures when applying hair dye. PPD is also used in photographic developer and lithographic plates and may cause an allergic contact dermatitis in photographers who work with these materials.

Most reactions to PPD occur several hours to days after the exposure.  Repeated exposures cause symptoms more rapidly and with increasing severity.  Reactions to PPD containing hair dyes may cause redness, irritation, blistering and swelling at the hairline and on the face.  The scalp itself is usually spared as the hair protects it from contact with the dye.  More severe reactions can cause a widespread rash, swelling, hives or rarely anaphylaxis.  Men who dye beards or moustaches may develop a rash in the centre of the face.  Reactions to tattoos cause skin irritation and inflammation 1-2 days after application and may result in long-lasting changes to skin colour.  A more wide-spread rash may occur after 1-2 weeks.

Individuals with PPD allergy may react to other components of dyes that have a similar chemical structure, such as para-toluenediamine found in many PPD-free semi-permanent hair dyes.  Azo dyes used in the clothing industry may also cause reactions due to cross-reactivity with PPD.

Patch testing can be used to confirm a dye allergy.  This test involves application of potential allergens to the skin by applying patches to the skin and observing if a rash develops over the next few days.

If you suspect a reaction to hair dye the hair should be washed with a soap substitute or mild shampoo.  Corticosteroid creams may be required to treat the inflammation and antihistamines may be useful to alleviate itchiness.  If the area becomes infected, antibiotics may be needed.  Permanent hair dyes should be avoided; however, most people will be able to use herbal hair dyes like henna.  It is important to carefully read labels and to be aware of cross-reactive allergens.  Hairdressers should practice safe dye application measures such as using gloves and emollients.  Public awareness need to be raised that black tatoos  can cause this type of allergy.