Can Allergens Remain in My Body?
The chemical p-Phenylenediamine is commonly used in hair dyes, just as you said. It is also found in textile dyes and is closely related to chemicals in black rubber and crude-oil derivatives. Professions at high risk for p-Phenylenediamine allergy include hairdressers, nurses, locksmiths, bricklayers, and farmers.
P-Phenylenediamine is one of dozens of chemicals that can cause contact dermatitis. Contact dermatitis is a form of skin allergy that generally affects areas of the skin that are in direct contact with the chemical. Noncontact areas of the skin and the rest of the body are not affected (i.e., contact with the chemical doesn't cause wheezing, nasal congestion, stomach symptoms, etc). Contact dermatitis usually appears as a red, angry patch of skin initially, which can blister and ooze clear or yellow fluid, and then heal and become dry and worn-looking over time.
It can be tricky to figure out the cause of contact dermatitis without patch testing, because there is usually a delay of one to two days between exposure and the onset of the rash.
Generally, if you are able to avoid the allergen, the rash eventually resolves (in days to weeks). The p-Phenylenediamine shouldn't stay in your body for years unless you had ongoing exposure. I did a little research on this chemical: There was one study that showed it lingered in the skin of rats that had been exposed to high levels. However, the study was conducted only over a few days and the skin in which the chemical was found was the area that was exposed initially, not some other part of the animals' bodies. This study doesn't really tell me much about whether the chemical can persist in the body. Despite this, I would think there are a handful of more likely explanations.
Without being able to see your rash, I would suggest the following possibilities:
1) There are many kinds of rashes. If the original rash is completely healed and this new one looks or acts differently and affects different parts of your body, it could well be an entirely different problem.
2) Because p-Phenylenediamine is found in many other products, you could have ongoing exposure that you aren't aware of. What about clothing dyes? This could be very difficult to sort out on your own. You would likely need the help of a dermatologist or allergist.
3) If you have one contact allergy, you may have others.
My advice would be to see a dermatologist who performs patch testing and has an interest in contact dermatitis. I think it is unlikely that your current problems are due to residual p-Phenylenediamine in your body, and I also think you will ultimately need to undergo patch testing to sort out what is going on. I hope this helps.
Last Updated: 04/07/2008
Allergy expert Dr. Anna Feldweg answers your frequently asked questions on allergy symptoms, diagnosis, treatment, medication, and management. Dr. Feldweg is a clinical instructor of medicine at Harvard Medical School and an attending physician at Brigham and Women's Hospital in Boston.