Which Chemical in Hair Dye Caused My Allergic Rash?

Published: January 3, 2020

Q: I recently dyed my hair, and ended up with a rash on my forehead, ears and scalp – and my eyes also swelled. My doctor said this is likely an allergy to the chemical para-phenylenediamine (PPD), and prescribed a corticosteroid ointment and hair rinse. Can you tell me more about this allergy?

Woman getting hair dyed.

Dr. Skotnicki: Allergy to PPD is common. It’s a chemical frequently used in salon and store-bought hair dyes to achieve natural-looking shades that don’t fade with shampooing.

With the help of ammonia, PPD reacts with the air and deposits pigment inside of the hair shaft at the cortex – a process that creates long-lasting results.

Allergic reactions to PPD range from mild – a rash on the top of the ears and eyelids – to severe, with swelling of the eyes and even the face. In more extreme cases, the chemical has even caused anaphylaxis.

If you are allergic to PPD, the good news is that there are PPD-free hair dyes.

Finding Safer Hair Dye

For a safer alternative, you would need to look for hair dyes that contain a related substance known as para-toluenediamine sulphate (PTDS). Only 25 percent of people allergic to PPD will react to this substance.

For instance, Clairol now has a hair dye with an “allergy gentle formula” and brands such as Goldwell, Schwarzkopf, L’Oréal and Wella also have specialty products that are PPD-free.

Many boxes of hair dye will state that they are PPD-free, but you still have to be aware of other related chemicals that will be problematic if you have PPD allergy. You can review a list of these on my blog at Drsandyskotnicki.com.

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