Hair dye allergy: PPD, ‘herbal’ colours and the 48-hour patch test

How permanent hair dye works

A box of permanent colour holds two things you mix just before use: a tube of colour cream and a bottle of developer.

• The colour cream holds small, colourless molecules called precursors, such as PPD, toluene-2,5-diamine or p-aminophenol, and couplers, such as resorcinol or m-aminophenol. It also holds an alkaliser: ammonia or, in ‘ammonia-free’ products, ethanolamine (MEA).
• The developer is hydrogen peroxide.

Once mixed, the alkaliser opens the outer layer of each hair and the small molecules slip inside. The peroxide makes them join up into much larger coloured molecules that are too big to wash back out. That is why the colour is permanent.

The same chemistry explains the risk. PPD and its relatives are small and reactive enough to get into skin too, where they bind to skin proteins, and the immune system can learn to treat that as an invader.

Henna and indigo work differently. They are plant powders that stain hair without a developer, and they do not need PPD to work.

The ingredients behind most reactions

PPD is one of the strongest skin allergens in everyday use. About 1.5% of the general population is allergic to it, and 4–6% of patients patch-tested in dermatology clinics. In Indian clinics it is consistently among the most common allergens: 54 of 80 people with suspected hair-dye dermatitis in Himachal Pradesh reacted to it. A survey of 159 hair dyes sold in India found PPD and resorcinol the most frequent sensitisers, and cartons often did not state the PPD content or carry proper warnings.

What a reaction looks like. It is a delayed reaction, appearing hours to days later, up to 72 hours after dyeing. Typical signs are itching, redness and weeping along the hairline, forehead, ears and neck. Severe reactions make the scalp, face, ears and eyelids swell, sometimes enough to need hospital care. In Indian users hair dye is also linked to dark patches on the forehead, temples and ears.

Why it can get worse. Each dyeing is a fresh exposure, so you can become allergic after years of uneventful use. Once you are, an ordinary 30-minute application is enough to set off a reaction. A mild itch after one colour is a warning, not something to push through.

Black henna. ‘Black henna’ or kali mehandi used for tattoos is henna mixed with PPD, sometimes at many times the strength in hair dye. It is a common way people, including children, first become allergic, and they tend to react more severely to hair dye later.

Cross-reactions. People allergic to PPD often react to related dye chemicals, some dark textile dyes and, less often, benzocaine-type numbing creams and sulfa medicines. Tell your doctor and pharmacist.

Use this table to read a label. The limit column is the EU maximum on the head after mixing, because the EU publishes one for each ingredient; India’s own limits for most of these are not public in the same way.

What ‘herbal’, ‘natural’ and ‘ammonia-free’ really mean

‘Herbal’ and ‘natural’ have no legal meaning for a hair colour in India. The Cosmetics Rules 2020 do not define either word, so the front of a pack tells you nothing about PPD. Studies keep finding PPD that the label does not declare in products sold as henna or natural dyes, and in some sold as ‘PPD-free’.

A quick plausibility check: pure henna stains orange-red to red-brown. A ‘herbal’ or ‘henna’ product that gives black or dark brown in one sitting is either blended with indigo or contains a synthetic dye. Look for p-Phenylenediamine, Toluene-2,5-Diamine or any other name in the table above.

‘Ammonia-free’ tells you only which alkaliser is used. Most ammonia-free colours use ethanolamine instead, which smells less but is still an irritant. Ammonia is not the allergen behind facial swelling, and an ammonia-free dye can carry exactly the same PPD.

‘PPD-free’ usually means a different PPD-type chemical. Most use toluene-2,5-diamine, which cross-reacts with PPD. ME+ is a genuine attempt at a lower-allergy molecule, but it still sets off reactions in a large share of people already allergic to PPD.

‘Ayurvedic’ is a licence for medicines, not a safety label. Under the Drugs and Cosmetics Act, an Ayurvedic medicine may contain only ingredients described in the classical texts. PPD is a synthetic dye, so a colour that contains it is not what most buyers expect when they read ‘Ayurvedic’.

What the law does require. Under Rule 37 of the Cosmetics Rules 2020, every hair dye with PPD or other such dyes must carry a caution that it may irritate skin, that a preliminary test should be made, and that it must not be used on eyelashes or eyebrows because that may cause blindness. Packs of 60 ml or 30 g or less are exempt from printing a full ingredient list, which covers many single-use sachets. In June 2026 the drug regulator, CDSCO, reminded every hair-colour maker and importer to follow these labelling and patch-test rules.

What the labels of popular colours say

We read the ingredient list of popular hair colours sold in India, from the pack photo or the brand’s own website, in October 2026. We list only products whose list we could read in full ourselves; formulas change, so check your own pack. Inclusion here is about ingredients, not a rating.

Every product above that lists PPD or PTD is legal to sell with the right warnings. The point is the gap between the front of the pack and the back: seven of them are sold on a herbal, natural, organic or Ayurvedic story and still carry a PPD-type dye. If you are allergic to PPD, the only products here that list no such dye are the plant-only ones, and even those deserve a skin test.

How to do a patch test properly

The pack test is a skin allergy test, also called an allergy alert test. It is not the same as a dermatologist’s patch test, but done properly it picks up most people who are already allergic.

1. Do it every time you colour, even with a product you have used for years. Allergy can develop at any point, and formulas change. India’s Cosmetics Rules say the test should be carried out before each and every application.
2. Do it at least 48 hours before you colour. The wording printed under Indian rules says to wash it off after 24 hours, but reactions can take up to 72 hours to show, and a 24-hour check misses some. Keep watching the spot until the moment you dye.
3. Use the exact product you will use, prepared as the leaflet says. Some brands test with the colour cream alone, others with a little mixed with developer.
4. Pick a spot behind the ear or on the inner forearm. Clean it with soap and water.
5. Apply a small amount and let it dry. Do not cover or rub it. Leave it as long as the leaflet says, then wash gently.
6. Check it at 48 hours and again just before you colour. Any itching, redness, burning, swelling, bumps or blisters at or around the spot means stop. Do not use that product, or any other permanent dye, until you have seen a doctor.
7. If nothing happens, go ahead carefully. Wear gloves, never leave the dye on longer than directed, and rinse your scalp well. A clear test lowers the risk but does not guarantee safety.
8. If you have already reacted to a hair dye or a black henna tattoo, do not self-test. The test puts a strong allergen on your skin. See a dermatologist instead.

Who should not colour their hair

Do not use a permanent or ‘herbal’ hair colour if:

• you have ever had a reaction after colouring your hair, however mild
• you have ever reacted to a black henna tattoo
• you have a rash on your face, or a sore, irritated or broken scalp
• your skin test was positive
• you have been diagnosed with a PPD or PTD allergy, unless a dermatologist has tested you with a specific alternative
• you are under 16; EU hair dyes must carry this warning

Never use hair dye on eyebrows or eyelashes. Do not put henna on babies or young children, especially if G6PD deficiency is known or suspected.

If you react

1. Wash it off at once with plenty of water and a mild shampoo.
2. Call 112 or go to an emergency department if your lips, tongue or throat swell, your throat feels tight, you are struggling to breathe or swallow, or you feel faint.
3. See a doctor the same day if your face or eyelids are swelling, your eyes are closing, or the skin is blistering or weeping.
4. For milder itching and redness, a pharmacist can suggest a soothing cream or an antihistamine; a doctor may prescribe a steroid.
5. Stop colouring until you have been tested, and ask for a dermatologist’s patch test once the reaction settles. Take the box with you.
6. Keep the pack and note the batch number. You can report it to your state’s drugs control department, which licenses cosmetics.
7. Tell every doctor, pharmacist and hairdresser that you are allergic to PPD.