Why do a Skin Allergy Patch Test?

Why do a Skin Allergy Patch Test?

Would you travel in a car without wearing a seatbelt? You may not get into an accident but it’s important to wear one as you do not know who is on the road.
The same principle applies to skin allergy patch testing – every person’s body is unique and the way the hair dye chemicals may affect you is also unique.

Firstly, the allergy to PPD is incredibly rare

What is para-phenylenediamine (PPD)? –  It is a chemical which makes hair go darker when it is exposed to the air and oxidises. This is the part of the colourant which can create a sensitivity in a person and result in an allergic reaction.
The other chemicals to look out for are para-toulenediamine also known as toulene 2,5 diamine, para-aminodiphenylamine
and 3-nitro-p-hydroxyethylaminophenol. If you have had a reaction to PPD then you are likely to react to these too.

If you have had a black henna tattoo it is essential to do a patch test as the black henna contains para-phenylenediamine. It also depends on what drugs (prescription and non-prescription) or antibiotics that could be in a person’s body. And if they have been using sunscreen or have a tattoo. All these things can alter the body’s way in which it can react.
If you get any reaction such as redness, stinging, contact dermatitis – contact your doctor immediately and do not ignore it.

The hair dye with the most PPD are black, dark brunette colours. They are in most permanent dyes and some semi-permanent dyes but not the wash in wash out hair dyes, which don’t require a developer, for example coloured shampoo.

If you are using bleach (a powder bleach mixed with hydrogen peroxide) it is still important to do a skin allergy patch test. Hydrogen peroxide can burn your skin – even when it is mixed to create a new compound – it is important to patch test.

As with all hair dyes always read the instructions and ingredient listing. If you are in a salon ask your hairdresser or colourist. AllergyUK have more information about cross-reactivity. http://www.allergyuk.org/skin-allergy/reactions-to-hair-dye

Disclaimer: Having a reaction from PPD is incredibly rare but if you have any doubts about hair dye ask your hairdresser or doctor.

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