Hair dye safety: is PPD the ingredient causing reactions?

A recent UK news report has raised concerns that a single aromatic chemical found in many permanent hair dyes could be behind a rise in adverse reactions. The ingredient under scrutiny is widely used to achieve rich, long-lasting colour results, and the piece suggests it appears in a large share of products on shelves. Here, we unpack what this means for salon professionals and at-home colour fans: what the ingredient is, what science and regulation say about its safety, how to recognise reactions, and practical steps to reduce risk without sacrificing your shade goals.

What’s the ingredient in focus — and why is it used?

The chemical most often linked to hair dye reactions is p-phenylenediamine (PPD), an aromatic amine frequently used in oxidative or “permanent” dyes. PPD helps darken and develop colour molecules inside the hair shaft when mixed with an oxidiser, which is why it’s been a cornerstone of long-wear formulas for decades. The recent report highlights claims that this single component features in a substantial proportion of hair dyes on the market. While that reflects PPD’s ubiquity in permanent systems, it doesn’t mean every dye contains it; semi-permanent and temporary colours often rely on different chemistries.

Importantly, PPD isn’t new to regulators. It’s among the most closely studied hair dye ingredients and is permitted for use in the UK and EU within strict concentration limits and with mandatory on-pack warnings. The reason for the oversight: although most users colour safely, PPD is a well-known skin sensitiser and can trigger allergic contact dermatitis in some people.

Allergic reactions: what the science and clinics see

Allergic contact dermatitis to hair dye typically appears as itching, redness, or a burning sensation on the scalp, hairline, ears, neck, or face within hours to a couple of days after application. In sensitised individuals, more pronounced swelling or blistering can occur. Extremely rare but serious reactions can involve facial swelling or breathing difficulties requiring urgent care. Dermatology clinics regularly patch test for PPD, and a meaningful minority of patients with suspected cosmetic allergies show sensitivity. Hairdressers, who handle dyes frequently, face a higher occupational risk of hand eczema unless they use robust protection.

Sensitisation can happen gradually: someone may colour their hair uneventfully for years, then suddenly react after the immune system learns to recognise the ingredient. Prior exposure via so-called “black henna” temporary tattoos — often illegally boosted with PPD to darken the stain — is a known risk factor for future hair dye allergy.

• Common early signs: tingling, itching, or tightness on the scalp or hairline.
• Typical delayed signs: redness, rash, or swelling around the ears, eyelids, and neck.
• Severe reactions (rare): pronounced facial swelling, wheezing, or widespread hives — seek emergency care.

It’s essential to distinguish irritation from allergy. Irritation can result from perfume, ammonia, or peroxide and tends to be immediate and non-immune. Allergy involves the immune system, can be delayed, and typically worsens on repeated exposures to the sensitiser.

What UK and EU rules say about PPD

Under retained EU/UK cosmetics law, PPD is permitted only in oxidative hair dye products and only up to defined limits in the final, ready-to-use mixture after mixing with developer. Labels must carry clear warnings, including the requirement to perform an allergy alert test 48 hours before use, even if the consumer has coloured before. Products also must display statements such as “Contains phenylenediamines” and caution against using the dye on eyelashes or eyebrows.

The Scientific Committee on Consumer Safety (SCCS) has repeatedly reviewed oxidative dye substances, including PPD and related compounds, and set conditions of safe use. While the committee acknowledges the sensitising potential, it concludes that with concentration caps, appropriate formulation, and the mandated warnings, the ingredients can be used safely for most consumers. Safety assessments are ongoing, and regulators periodically update ingredient lists as new data emerge.

What this means practically: when you follow directions, conduct allergy alert tests as instructed, and avoid colouring during scalp flare-ups or if you’ve ever had a reaction, the risk of severe harm is low — but not zero, particularly if you’re already sensitised.

Reducing risk: smart steps for colour fans and pros

Colour can absolutely be part of a healthy hair journey, provided you take the right precautions. Whether you colour at home or in a salon, the following measures help reduce risk, respect sensitive scalps, and preserve great results.

• Always do the allergy alert test 48 hours before every colouring session, exactly as the leaflet describes. If you react — even mildly — do not proceed.
• Never use permanent dye on broken, irritated, or inflamed scalp. Postpone colouring until the skin barrier has recovered.
• If you’ve had a black henna tattoo, be extra cautious. Discuss with your stylist or GP/dermatologist and consider patch testing with a specialist.
• Consider alternatives if you’re concerned: semi-permanent or temporary colours often avoid PPD, though they may still contain other sensitisers. Always review the ingredient list.
• Protect skin during application: apply a light barrier around the hairline and wear gloves. Avoid excess overlap onto skin.
• Rinse thoroughly after processing, and follow aftercare to minimise scalp residue.
• Keep a colour diary: note products, shades, and any sensations to identify patterns early.

For salon professionals, occupational skin disease is preventable with the right controls. Rotate tasks where possible, use high-quality nitrile gloves (double-glove for wet work), change gloves regularly, and cleanse hands with mild, fragrance-free products. Maintain ventilation, follow manufacturers’ instructions meticulously, and keep patch-test records. If a client reports even a mild prior reaction, pause and reassess — it’s better to perform further testing or recommend non-oxidative options than risk escalation.

Sorting fact from fear: what about “PPD-free” claims and new chemistries?

“PPD-free” does not automatically mean “risk-free.” Some PPD-free permanent dyes use chemically related ingredients (for example, other aromatic diamines) that can still cause allergies in susceptible individuals. Cross-reactivity can occur. Semi-permanent and temporary dyes generally avoid oxidative chemistries and may be an option for those with prior reactions, but it’s vital to patch test and scrutinise labels regardless.

Industry scientists continue to explore modified dye molecules designed to reduce sensitisation potential, along with improved delivery systems that limit scalp contact. While promising, no system can guarantee zero risk of allergy. That’s why the foundational safety pillars — responsible formulation, clear labelling, and user vigilance — remain essential.

When to see a professional

If an allergy alert test produces redness, swelling, or itching, do not colour and seek advice from a pharmacist or GP. Persistent or severe rashes around the hairline and ears warrant dermatology input; patch testing can pinpoint the culprit and guide future choices. If you experience facial swelling, difficulty breathing, or dizziness after using hair dye, call emergency services immediately.

Key Takeaways

• PPD is a common ingredient in permanent hair dyes and a recognised skin sensitiser; most people use it safely, but some develop allergies over time.
• UK/EU law permits PPD with strict limits and requires allergy alert testing and clear warnings on-pack.
• Perform a 48-hour allergy alert test before each use, avoid colouring on irritated scalp, and rinse thoroughly.
• “PPD-free” doesn’t guarantee zero risk; always check labels and consider semi-permanent options if sensitised.
• Seek medical help for severe reactions; dermatology patch testing can confirm sensitivities and inform safer choices.

Frequently Asked Questions

Does every hair dye contain PPD?
No. PPD is common in permanent oxidative dyes, especially darker shades, but many semi-permanent and temporary colours don’t use it. Always read the ingredient list and warnings.

Is the allergy alert test the same as a dermatology patch test?
No. An allergy alert test follows the product leaflet and checks for an immediate reaction to that specific formula. A clinical patch test is a medical procedure that evaluates sensitivity to individual chemicals, including PPD and related substances.

Can I develop an allergy after years of trouble-free colouring?
Yes. Sensitisation can occur over time. A product you tolerated before can eventually trigger a reaction, which is why pre-use testing and caution matter.

I’ve had a black henna tattoo in the past. Should I avoid permanent dyes?
Black henna often contains high levels of PPD and may predispose you to allergy. Speak to a healthcare professional and consider medical patch testing before using permanent dyes.

Are ammonia-free dyes safer for allergies?
Ammonia-free relates to odour and cuticle opening chemistry, not necessarily allergenicity. Allergies are more commonly linked to dye intermediates like PPD, not the alkaliser. Check labels carefully.

What should salons do if a client reports a past reaction?
Pause service, record details, and consider alternatives that avoid the suspected allergen. Discuss medical patch testing and never proceed without a successful, recent allergy alert test.