It is wedding and festival season, and that means fresh colour for greying roots and mehndi on every pair of hands. For most people both are uneventful. But every season, dermatologists see the same story: a dye used for years, or a dark “instant” mehndi, followed a day later by an itchy scalp, puffy eyelids, or a face so swollen the eyes barely open.
The usual culprit has a name: PPD. This guide explains how the allergy shows, what to do straight away, when it’s an emergency, and how to colour your hair more safely.
What PPD is, and where it hides
PPD (para-phenylenediamine) is the ingredient that makes permanent hair dyes work, especially in black and dark brown shades. It is colourless in the pack and turns into dye when it meets the developer. Darker shades usually contain more of it.
PPD also turns up in:
- Black mehndi, “kala mehndi” and instant dark henna for hands and temporary tattoos, where it is added to darken the colour and make it stain faster;
- beard and moustache dyes;
- some dark cosmetics, textile dyes and black rubber.
Pure henna stains orange to reddish brown and takes hours to develop. A paste that gives a jet-black stain within an hour very likely contains PPD.
How an allergy develops
PPD allergy is a delayed allergic reaction (allergic contact dermatitis). It builds up with repeated contact, which is why:
- the first use often causes nothing, and the allergy appears after months or years of the same dye;
- each new exposure tends to cause a stronger, longer reaction;
- a black mehndi tattoo can make you allergic, and a later hair dye then triggers the reaction;
- once allergic, the allergy usually stays for life.
Studies from India report PPD as one of the more common allergens on patch testing here, and a sizeable share of regular hair dye users report some skin problem from it.
Signs of a reaction
Symptoms usually start hours to two or three days after dyeing, not during it.
Mild to moderate:
- itching, burning or tightness of the scalp, hairline, ears or neck;
- a red, dry or flaky rash; on brown skin it may look darker brown, purple or grey rather than red;
- puffy upper eyelids, often the first place to swell;
- oozing or small blisters along the hairline;
- on the hands after black mehndi, a raised, itchy, blistering copy of the design, sometimes leaving a pale or dark mark for months.
Severe:
- marked swelling of the face, eyelids and scalp, with blisters and oozing;
- a rash that spreads beyond the scalp to the face, neck and body.
Emergency signs (rare): swelling of the lips, tongue or throat, wheezing, difficulty breathing or swallowing, feeling faint. Call 108 or go to the nearest emergency department straight away.
The slow kind: darkening without much itch
On brown skin, a repeated low-grade reaction can show mainly as pigmentation: grey-brown darkening of the forehead and temples, around the hairline, over the ears or the sides of the neck, building up dye after dye. Indian studies have found hair dye use common among people with this kind of facial darkening. Because it itches little, people often blame the sun and reach for lightening creams while the real trigger continues every month. Our guide to dark spots and pigmentation covers the other causes.
What to do in a reaction
- Wash it out now. Wash the hair and scalp thoroughly with a mild shampoo and plenty of lukewarm water, more than once, to remove as much dye as possible. For mehndi, wash the skin with soap and water.
- Don’t add anything else. No more dye to “cover” it, no lemon, toothpaste, home pastes or creams from a friend.
- Cool and calm. Cool compresses and a plain moisturiser can ease mild itching; a non-drowsy antihistamine may help the itch.
- Get help fast for swelling. Puffy eyes, a spreading rash, blisters or oozing need a doctor the same day: a short course of prescription treatment settles most reactions and limits darkening afterwards.
- Write down the product, shade and brand, or photograph the box. It helps the doctor and protects you next time.
Avoid using strong steroid creams from the chemist on your face for weeks on end; our post on steroid creams on the face explains why a short, supervised course is different from long self-treatment.
Is it allergy or irritation?
Not every sting is an allergy. Dyes, bleaches and developers are alkaline and can irritate: stinging or burning within minutes of applying, usually only where the product sat, settling within a day or two. Allergy is delayed (hours to days), itchier, and spreads to the eyelids, ears and face. Both are worth avoiding, but an allergy decides what you can use in future. Hair colouring can also leave the hair dry and breakable; that is a hair care problem rather than a skin reaction.
A dermatologist can confirm a PPD allergy with patch testing, using standard test strengths on the back; at OrnaSkin, patch testing is done when it’s needed. That also helps you know whether any alternative dye is likely to suit you.
Colouring more safely
If you have never reacted:
- Do the skin test on the pack, 48 hours before every colouring, as the instructions say.
- Leave the dye on no longer than stated, and rinse very thoroughly.
- Smear petroleum jelly along the hairline, ears and neck, and wipe off any dye that touches the skin.
- Wear gloves, and choose lighter shades and less frequent touch-ups where you can.
- Skip black mehndi, especially for children; it is the commonest way people first become allergic.
If you have reacted before:
- Stop using permanent dyes containing PPD, and tell your salon.
- Don’t self-test with the same dye “to check”; a test can trigger a strong reaction.
- Don’t assume “PPD-free” or “herbal” means safe; read the ingredients and ask a dermatologist. Related dyes such as toluene-2,5-diamine still cause reactions in many PPD-allergic people.
- Pure henna (and some plant-based colours) is the lower-risk option, though it gives a reddish tone and isn’t permanent.
- Mention the allergy to every doctor: a few medicines and local anaesthetics are chemically related to PPD.
When to see a dermatologist
- A reaction with swelling of the face or eyelids, blisters or oozing (same day; emergency signs need 108);
- an itchy scalp or hairline that returns after every colouring;
- darkening of the forehead, temples, ears or neck since you began dyeing;
- a mark left by black mehndi that hasn’t faded after a few weeks;
- you want to know which dyes, if any, you can use safely.
At OrnaSkin, the dermatologist examines the rash, settles the reaction, arranges patch testing when it’s needed, plans care for any darkening left behind and advises on safer colouring. See our dermatology consultation page, and our guide to psoriasis and eczema for other itchy, red rashes. Planning for a wedding? Our bridal skincare timeline shows when to fit in colouring and treatments.
The short version
Most hair dye allergies are caused by PPD, also found in black mehndi. A reaction comes hours to days later, with itch, redness or puffy eyelids, and gets stronger with each exposure. Wash the dye out at once, see a doctor the same day for swelling, and call 108 for lip, tongue or throat swelling or breathing trouble. Do the pack’s skin test every time, skip black mehndi, and if you’ve reacted once, stop PPD dyes and ask a dermatologist what is safe for you.
