Hair-dye reactions: PPD, testing and warning signs
Recognise a possible reaction, follow the product's safety instructions and distinguish a home test from medical assessment.
Do not cover a reaction with another colouring treatment
Burning, itching, a rash or swelling after colouring is not a reason to try a stronger product. Stop using the suspected product and follow its safety instructions. Seek medical advice for persistent, worsening or significant symptoms. Keep the packaging so the ingredients can be checked.
If breathing becomes difficult, the tongue or throat swells, someone collapses or symptoms rapidly worsen, call 112 in the EU. Do not wait for a cosmetic customer-support reply. This guidance does not diagnose a particular reaction.
What PPD means
PPD, or paraphenylenediamine, is used in many permanent and some other hair dyes and can cause an allergic reaction. Previous exposure to a black henna tattoo is relevant information to share with a clinician. The word henna by itself does not guarantee a known or harmless composition.
Symptoms need not begin immediately. The NHS notes that hair-dye reactions may take up to 72 hours to appear. Timing alone does not prove that a dye caused every later symptom, but recent applications belong in the history you give a healthcare professional.
A home test is not a medical diagnosis
If the manufacturer requires testing before use, follow the exact method and waiting time. Do not invent a quicker version. A home test is not a complete allergy investigation and does not cancel a previous reaction.
Consult a dermatologist about suspected allergy and whether professional testing is appropriate. A milder smell or an ammonia-free label is not a sufficient safety criterion. Hair-fibre damage and skin allergy are separate subjects.
Prepare useful information
Keep the product name, packaging and ingredient list. Record where and when it was applied, when symptoms started and which other new products were used. Mention previous reactions and black henna exposure. Photographs may help describe the course, but cannot replace assessment.
Natural origin is not a guarantee of suitability. Plan further cosmetic use around the advice you receive, rather than assuming another marketing category will be safe.
