Henna (black) allergy
Contact allergy to PPD-adulterated black henna tattoos.
About henna (black) allergy
Natural henna is a plant dye that rarely causes problems, but so-called black henna, used for temporary skin tattoos, is a different matter. It is frequently adulterated with paraphenylenediamine (PPD), a potent hair-dye chemical added to darken the colour and speed drying. PPD is a strong sensitiser causing delayed, type IV allergic contact dermatitis, so a reaction usually appears within a few days of the tattoo. These tattoos are often applied on holiday or at markets without ingredient controls, and a single exposure can leave a person sensitised for life.
The reaction can be striking, with an itchy, red, blistered or weeping rash forming in the exact shape and outline of the tattoo design, sometimes leaving pale or dark marks and even scarring once it settles. Because the trigger is PPD, people sensitised by black henna are then at high risk of severe reactions to PPD-containing hair dyes, and may cross-react with related azo dyes, some rubber chemicals and certain local anaesthetics.
Diagnosis is by patch testing with a dermatologist, which confirms PPD sensitivity; skin-prick testing is not used. The essential advice is to avoid black henna tattoos altogether and, once sensitised, to avoid PPD hair dyes and related chemicals for life. Acute flares may need emollients and topical or, occasionally, oral steroids under medical guidance. See your GP promptly if a henna tattoo becomes blistered, spreading or severe.
Common triggers
- Henna (black) and products containing it
Symptoms
- Red, itchy rash (contact dermatitis)
- Dry, cracked or scaly skin
- Blistering or weeping in severe cases
- Burning or stinging where skin met the trigger
Avoidance & management
- Avoid skin contact with the trigger
- Wear gloves or use barrier creams
- Choose products labelled free from the allergen
- Rinse skin promptly after contact
- Use emollients or prescribed steroid creams
Sources & references
Allergy safety: what everyone should know
Mild-to-moderate reaction signs
- Itching, hives or a raised rash
- Swelling of lips, face or eyes
- Tingling mouth, sneezing, runny nose
- Stomach pain, nausea or vomiting
Anaphylaxis — call 999 (UK) or 112 (EU) immediately
- Difficult or noisy breathing, wheeze, persistent cough
- Swelling of the tongue or tightness in the throat
- Dizziness, collapse, pale and floppy (young children)
- Use an adrenaline auto-injector (e.g. EpiPen) at once if prescribed, then call an ambulance even if symptoms improve
Allergy or intolerance? A true allergy involves the immune system and can escalate quickly; an intolerance (e.g. lactose intolerance) is unpleasant but not life-threatening. The symptoms overlap, so self-diagnosis is unreliable.
Getting tested: home-testing kits based on IgG are not diagnostically valid. If you suspect an allergy, ask a GP for referral to an allergy clinic for skin-prick or specific-IgE testing and a supervised food challenge where appropriate.