Reaction to hair dye
Millions of people colour their hair for years without the slightest trouble. In some, though, dye eventually provokes a reaction: from mild itching of the…
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Medicines commonly prescribed for Reaction to hair dye
For informational purposes only. Always consult a doctor before using any medicine.
Dosage form: TABLET, 10 mgActive substance: cetirizineManufacturer: Teva Pharma S.L.U.Prescription requiredDosage form: TABLET, 10 mg/coated tabletActive substance: cetirizineManufacturer: Towa Pharmaceutical S.A.Prescription requiredDosage form: TABLET, 10 mg cetirizine dihydrochlorideActive substance: cetirizineManufacturer: Ucb Pharma S.A.Prescription required
Millions of people colour their hair for years without the slightest trouble. In some, though, dye eventually provokes a reaction: from mild itching of the scalp to swelling of the face that seals the eyes shut and, rarely, to a state that needs an ambulance. What separates one outcome from the other is usually a single thing — whether the person noticed the first faint signs and stopped, or carried on colouring because "it itched a bit, but it passed". Here is what in the dye causes the trouble, how irritation differs from allergy, and what to do once a reaction has started.
What actually causes the reaction
The main culprit is paraphenylenediamine, listed on the box as PPD or p-Phenylenediamine. It is an oxidative dye: it enters the hair almost colourless and darkens inside it, which is why the colour lasts until the roots grow out. No permanent dye yet achieves the same result without substances from this family.
Three things are worth knowing.
- The darker the shade, the more dye it contains. Jet black and dark brown come up most often in accounts of severe reactions; light shades and bleaches come up least.
- PPD is not alone. Formulations contain relatives of it — toluene-2,5-diamine, sometimes marketed as the gentle alternative, along with resorcinol and aminophenols. Someone allergic to PPD may react to these just as strongly, because the immune system recognises a similar molecule.
- Besides the dye itself, hydrogen peroxide and ammonia irritate the skin. They do not cause allergy, but they sting, dry the scalp and leave tiny cracks, and dye passes through damaged skin far more easily.
The amount of PPD allowed in home colourants is capped by law, and used as instructed these products are reasonably safe for most people. The problem is not the dye but the fact that allergy is a property of the individual, and it can appear at any application, the first or the hundredth.
Irritation and allergy are not the same thing
The two are constantly confused, and what you should do next differs completely.
Irritation begins during the application or straight after it: the scalp stings and burns and turns red exactly where the product sat. It settles within a day or two of rinsing off. It tends to hit those who scratched their scalp beforehand, colour freshly washed hair, or leave the mixture on longer than stated.
Allergic contact dermatitis behaves differently, and that is the trap. It comes on with a delay, usually about forty-eight hours later and sometimes longer, by which point the person no longer connects it with the dye. It shows itself as:
- itching and redness not only under the hair but along the hairline, on the temples, behind the ears, on the neck and on the eyelids;
- swelling of the eyelids and the face, at times very marked;
- small blisters, weeping and crusting, later scaling and cracks;
- a tight, burning feeling in the skin that refuses to settle for several days.
An allergy does not fade because you colour less often. Every subsequent application meets an immune system already primed against the dye, and the reaction is usually worse than the last one. That is why mild itching after colouring should not be put down to chance: it is a warning, not a trifle.
Separate from all this is the immediate type of reaction — nettle-like weals and swelling of the lips and eyelids within the first minutes. It is less common, but it is the one that turns dangerous.
Signs that mean calling an ambulance
A severe allergic reaction unfolds within minutes and calls for help, not observation. Call an ambulance (in Europe the single number 112) if during colouring or shortly afterwards any of the following appears:
- difficulty breathing, wheezing, a feeling that the throat is closing;
- a hoarse, altered or lost voice, trouble swallowing, a sense that the mouth is swollen;
- swelling of the lips, tongue, eyelids or face;
- a nettle rash spreading over the body, with pale, cold, clammy skin;
- sudden weakness, dizziness, vision going dark, fainting;
- sudden abdominal pain and vomiting alongside the rash and swelling.
While help is on the way, rinse the dye off with cool water if that is possible without leaving the person unattended. If an adrenaline auto-injector is available, use it at once rather than waiting for things to worsen: in a severe reaction, delay is more dangerous than an extra dose. Lay the person down and raise their legs, but let them sit up if lying flat makes breathing harder. They must not stand up abruptly after the injection. Even once they feel better, hospital assessment is needed, because the reaction can return several hours later.
The test before colouring
Manufacturers ask for a test about forty-eight hours before every application, and that is sound advice even with a familiar brand. Mix a small amount of product as instructed, apply it to clean dry skin behind the ear or in the crook of the elbow, let it dry and leave it alone. Looking after ten minutes is not enough: check the spot the next day and again at forty-eight hours, because allergy declares itself late. Any redness, itching, blistering or burning there means the product must not be used.
Its limits matter too. The test guarantees nothing: a quiet result lowers the risk without abolishing it. If you have already reacted to dye in the past, there is no point repeating the test at home — you will simply reproduce the reaction somewhere else. What makes sense then is a dermatologist and proper patch testing: a panel of substances is taped to the back and read twice, at forty-eight and at ninety-six hours. You leave with a list of what to avoid, and it extends well beyond hair products.
Black henna tattoos, a short cut to serious allergy
Genuine henna gives an orange-brown design, takes a long time to apply and fades within days. What is sold in holiday resorts as "black henna" is something else: PPD is added to the paste, sometimes at concentrations unthinkable in a hair colourant. The design comes out coal black within an hour and lasts longer.
The price can be double. Inflammation often develops precisely along the outline of the design, leaving marks or fine scars that persist for months. More importantly, that dose of dye can make a person allergic to PPD for life: from then on, the very first ordinary colouring may bring on a reaction that was nowhere in evidence before. The saddest cases are children, who are the ones most often given these designs.
If the reaction has already begun
Start by rinsing off the remaining dye with cool water and a mild shampoo, without scrubbing the skin with a flannel or towel. After that:
- an unperfumed moisturiser on the affected skin several times a day, which eases the tightness and speeds healing;
- cool compresses on the eyelids if the face has swollen;
- topical corticosteroids help when inflammation is marked, but on the face and eyelids they are used only on a doctor's instruction and in short courses;
- antihistamines reduce itching and the rash on the body; a doctor or pharmacist can help you choose one;
- do not scratch the scalp and do not try to "fix" things by colouring over with another shade — any further application now will only intensify the reaction.
See a doctor the same day if the facial swelling is increasing, if a large area of skin is involved, if pus is seeping from under the crusts, if there is an unpleasant smell or if a temperature develops, because that means infection has set in. Severe dermatitis sometimes needs a short course of oral steroids, and that is a decision for the doctor.
What to colour with if PPD is out
There is no entirely harmless substitute, but there are options, and the more carefully you read labels the wider they get.
- Bleaching and going blonde manage without oxidative dyes, though peroxide still irritates the skin.
- Colour-depositing shampoos, toning masks and semi-permanent dyes may be free of PPD, but not by default: the ingredient list has to be read, and related substances looked for in it.
- Natural henna and indigo suit many people, but plant material can also cause allergy, and mixtures with additives are often sold under the name of henna.
- Highlights and techniques that keep the product off the scalp reduce contact, yet with an established allergy they are not enough: fumes or an accidental smear will do it.
One more detail rarely gets a mention. Substances structurally close to PPD turn up in textile dyes, black rubber, some local anaesthetics and sulfonamide medicines. If PPD allergy has been confirmed, tell your doctor and your dentist, because it occasionally influences the choice of drug. And always mention it at the salon: hairdressers' own hands suffer from dyes more than their clients' do, and gloves are no formality for them.
Online consultation
A remote appointment handles precisely the situation where people get stuck: the redness did not appear straight away, the itching comes and goes, and it is unclear whether this is leftover irritation or the beginning of an allergy. From your account and a few photographs the doctor works out what is happening, advises on calming the itch and the swelling, on whether a topical steroid is needed, and on whether patch testing is worth arranging. It is also a good moment to go through the ingredient list of your dye and decide what to colour with from now on. The severe signs listed above are not assessed through a screen: those mean an ambulance straight away.
This material is for information only and does not replace medical advice.
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