Hair Dye Allergies and Patch Tests

The main cause of allergic reactions to hair dye is PPD (paraphenylenediamine), a dye chemical found in many permanent and some semi-permanent hair dyes. A reaction can take up to 72 hours to appear, which is why the FDA says to do a skin patch test every time before you dye your hair, even with a product you have used before. People who have reacted to hair dye before, or who have had a "black henna" tattoo, are at higher risk.

This page is general information, not medical advice. It is part of our guide to ways to cover gray hair.

What causes hair dye allergy

PPD is the main cause. The FDA says PPD "has been implicated more prominently in leading to allergic reactions," and a 2014 review in Actas Dermo-Sifiliográficas calls it the main cause of allergic contact dermatitis from hair dyes. Allergic contact dermatitis is a rash caused by an allergy to something that touched the skin.

PPD is also used outside hair dye. DermNet, a dermatology reference site, lists textile and fur dyes, "black henna" tattoos, printing inks and black rubber among its other uses. The FDA adds that people who are sensitive to PPD may also react to some textile dyes, rubber products, anesthetics and other medicines. This is called cross-sensitization.

Allergy can develop over time. The FDA says people can develop sensitivities with repeated exposure, so a dye you used for years without trouble can still cause a reaction.

Not every reaction is an allergy. A 2018 review in the International Journal of Trichology notes that hair coloring can also cause hair loss and irritant dermatitis, which is skin damage from a harsh substance rather than an immune response. The 2014 review also mentions occasional reports of allergy to ingredients in temporary hair dyes, such as quinine.

Symptoms and when they appear

The NHS says hair dye reactions are fairly common but usually mild. It lists these common skin reactions:

• stinging and burning
• an itchy rash
• dryness, tightness and soreness
• blisters

On white skin, a rash can look red. On brown and black skin, the NHS says it may look darker brown, purple or gray, or be harder to see. DermNet says a mild allergy may show as an itchy, dry rash on the upper eyelids or the rims of the ears, while more severe reactions cause marked redness, blistering and swelling of the eyelids, scalp, face and neck. Reactions appear from a few hours to a few days after contact, according to DermNet, and the NHS says symptoms can take up to 72 hours to appear.

Severe reactions are rare, but they are an emergency. The NHS lists these warning signs: sudden swelling of the lips, mouth, throat or tongue; fast breathing or struggling to breathe; a tight throat or trouble swallowing; skin, tongue or lips turning blue, gray or pale; sudden confusion, drowsiness or dizziness; or fainting. If you notice any of these, call emergency services right away (999 in the UK, 911 in the United States).

Who is at higher risk

• People who have reacted before. In the UK, labels on dyes with PPD must tell you not to color your hair if you have ever reacted after coloring it.
• People who have had a "black henna" tattoo. The NHS and the FDA both warn that these tattoos contain PPD, which raises the risk of a reaction to hair dye.
• Hairdressers and their clients. DermNet names hairdressers, who may apply dye several times a day, and clients who use darker shades.
• People with skin of color. DermNet says PPD allergy is more common in people with skin of color than in people with light skin.
• People under 16. UK labels on dyes with PPD must say the product is not intended for anyone under 16.
• People with an irritated scalp. The FDA says not to dye your hair if your scalp is irritated, sunburned or damaged.

The skin test at home

In the United States, the FDA calls synthetic hair dyes, whether permanent, semi-permanent or temporary, "coal-tar hair dyes." They do not need FDA approval, but the FDA can take action against one that lacks this caution statement or directions for a skin test:

Caution - This product contains ingredients which may cause skin irritation on certain individuals and a preliminary test according to accompanying directions should first be made. This product must not be used for dyeing the eyelashes or eyebrows; to do so may cause blindness.

Follow the directions for your product. The FDA says to do a patch test on your skin every time before you dye your hair. The NHS suggests testing the dye on a strand of hair at least 48 hours before you use it, and buying a patch test kit if you think you may be allergic.

Watch your skin during and after the test. The American Academy of Dermatology (AAD) says that a rash, redness, swelling, burning or itching means you are having an allergic reaction. If that happens, do not dye your hair, and see a dermatologist about further allergy testing.

A dermatologist's patch test

After a reaction, a dermatologist can find out what caused it. The AAD explains that patches with possible allergens are placed on your back and left there for 48 hours. You should not shower or scratch while they are on, or the test may miss something. After the patches come off, you return 4 to 7 days later, because allergic reactions can take time to develop.

DermNet says PPD is tested at 1 percent in petrolatum, a type of petroleum jelly. A clear positive result means an allergic reaction to permanent dyes with PPD will most likely happen.

If you are allergic to PPD

DermNet advises people with a confirmed PPD allergy to avoid all oxidation-type hair dyes, which include permanent and demi-permanent dyes. It reports that about 10 percent of people allergic to PPD also react to semi-permanent dyes, and that dyes using para-toluenediamine sulfate (PTDS) instead of PPD are tolerated by about half of them. The other half still react, so ask a doctor before you try one.

The NHS suggests choosing a non-permanent hair dye if you have reacted to a permanent one, avoiding products with PPD, and wearing gloves. The FDA advises reading the ingredient statement to make sure that ingredients that caused you problems in the past, such as PPD, are not present.

Henna is a separate case. The FDA lists henna as a color additive approved for hair, but "black henna" is different and contains PPD. Gradual hair color explained covers henna in more detail.

What the rules say on labels

Rule	Where it applies	What it requires
Caution statement	United States	Coal-tar hair dyes carry the statement quoted above and directions for a skin test
Allergy warnings on dyes with PPD	United Kingdom	Labels must say "Hair colourants can cause severe allergic reactions," that the product is not for people under 16, and that "black henna" tattoos may increase your risk
Limit on PPD	United Kingdom	No more than 2 percent PPD in the mixed product applied to the hair
Banned and restricted substances	European Union	181 substances banned from hair dye products, and 114 allowed only with restrictions (European Commission)

When to get help

• Mild symptoms: wash your hair and scalp right away with a mild shampoo, as the NHS advises. A pharmacist can suggest a moisturizing cream or antihistamine tablets or cream.
• Symptoms that get worse: the NHS advises seeing a GP (a family doctor).
• Severe symptoms: call emergency services right away.
• After any reaction: the FDA asks you to tell your healthcare provider and then report the problem to the FDA.

For a step-by-step plan that includes the skin test, read covering gray at home for the first time. The dye types are explained in permanent, demi-permanent and semi-permanent dye and root touch-up products.

LIUMIQ is developing a gradual color product for gray hair. It is not for sale yet. You can join the waitlist to follow the work.