P-phenylenediamine, PPD for short, is a commonly used black dye used in products spanning from hair dyes to printer ink. It is also one of the more common contact skin allergens. Allergic contact dermatitis is an allergic reaction where you can get a rash days after coming into contact with an allergen. In fact, Sweden and France banned PPD at one point because PPD hair care products were causing so many cases of contact allergies! Today, PPD is still used in hair care products, just at a lower concentration. However, even these lower levels of exposure seem to be enough to sensitize patients with a black dye allergy to cause a contact allergy over time.
Rick is an older gentleman who comes into the office complaining of an inflamed and itchy region along his scalp and neck. Not much is new in Rick’s life. This past week, he has been busy with work and dyed his hair black about 4 days ago as he usually does.
Tammy is a hairdresser who has been working at a local salon for several years. She comes in after having a rash on her hands and arms over the past month. She has never had this rash before although she noted that it got better when she went on vacation.
In these cases, we would be suspicious of Rick’s hair dye and Tammy’s job as a hairdresser as a potential cause for their rashes. Real cases are usually much more complicated than these simplified stories, but they don’t have to be. If these stories sound similar to yours, it might be worth investigating if you have allergic contact dermatitis to PPD.
It is safe to say now that you get the point: PPD is found in permanent hair dyes, especially black hair dyes. It is estimated to be in approximately 70% of all hair dye products. However, PPD is also present in other things as well. Black rubber, fur dyes, printer’s ink, photographic chemicals, X-ray film fluids are all additional sources of PPD.
Have you ever get one of those ornate, black ink temporary tattoos? Did you get a rash after? You might be allergic to PPD. More recently, studies have found PPD in henna ink, specifically black henna mixtures. When used for skin painting, the dye and PPD remain on the skin for a long time. This can make people become sensitized and develop an allergic contact dermatitis over time.
As with any contact allergen, itching and rashes occur at the site of contact. Since often times hair dyes are the trigger, people will get itching, redness, and scaling on their scalp and neck like Rick. In more severe cases, these lesions can even progress to blistering. Hairdressers that frequently work with hair dyes can get reactions on their hands like Tammy. People using using henna containing PPD will get symptoms around their body painting.
What is the treatment?
Avoidance is the best policy. Luckily PPD is a little easier to avoid than some of the other contact allergens we have written about. There are some hair dyes that are PPD free. However, patients should be aware that “PPD free” hair products might still contain phenylenediamine variants like Toluene-2,5-diamine sulfate which may still cause a reaction. They are chemically related.
Recently some safer non-PPD hair coloring agents have come out. However, you should always read labels before using a product because company formulations can change over time.
Do you have a severe rash now? There are some things you can do in the meantime until you figure out the cause. Barrier creams are act as strong moisturizers. Applying barrier creams, like Vaniply, can help prevent the allergen from reaching your skin. Meanwhile, topical steroids can be used to reduce the severity of your rashes.
If you think PPD is causing your rash, you can try avoiding the products we have listed above and see if the rash goes away. For example, in our cases above Rick could try not using a black hair dye. If the rash comes back when you reuse the substance, then you may have found your culprit.
If you are unsure whether or not you have a PPD allergy (contact allergens can be tricky! You can talk to your dermatologist about patch testing. Patch testing is used to help doctors determine whether you have a true skin allergy (allergic contact dermatitis) or an irritant contact dermatitis. This is determined by putting together your history, your job, your exposure, the environment, and your patch testing results.
Le Coz, C. J., Lefebvre, C., Keller, F., & Grosshans, E. (2000). Allergic contact dermatitis caused by skin painting (pseudotattooing) with black henna, a mixture of henna and p-phenylenediamine and its derivatives.Archives of dermatology, 136(12), 1515-1517.
Schalock, PC. Common allergens in allergic contact dermatitis. In: UpToDate, Post TW(Ed), UpToDate, Waltham, MA. (Accessed on March 30, 2016.)
Thyssen, J. P., & White, J. M. (2008). Epidemiological data on consumer allergy to p‐phenylenediamine. Contact Dermatitis, 59(6), 327-343.