Permanent hair dye linked to health risks, report warns

A new report covered by WalesOnline has raised concerns that frequent use of permanent hair dyes could generate hazardous byproducts and be linked to three key health issues. While cosmetic formulas sold in the UK are regulated, the findings renew attention on allergic reactions, respiratory irritation and long‑term risks that continue to be studied. Here, we break down what the report means for everyday colour users, how oxidative dyes work, who may be most at risk, and the safer habits worth adopting without alarm.

What the new warning covers — and what it doesn’t

The coverage highlights scientific concern that the chemistry of permanent (oxidative) dyes can produce potentially hazardous byproducts during colouring. The three areas of health focus are:

• Allergic contact dermatitis: Skin reactions to hair dye ingredients, most notably p-phenylenediamine (PPD) and related aromatic amines.
• Respiratory irritation: Fumes and vapours from dyeing (including developers) that may aggravate breathing, especially in enclosed or poorly ventilated spaces.
• Long‑term risks under investigation: Ongoing research into potential associations between long‑term dye exposure and certain cancers, especially in occupational settings. Evidence for personal home use remains mixed and continues to be evaluated.

It’s important to keep two truths in view at once: UK/EU‑compliant dyes are assessed for safety when used as directed, and many people colour their hair without incident. At the same time, allergic reactions are well documented, and occupational exposure for hair professionals requires careful precautions. The latest discussion is not a call to panic but a prompt to use colour safely and stay informed as science evolves.

The science of permanent colour: why byproducts can form

Permanent hair colour relies on oxidative dye chemistry. Typically, small dye “precursor” molecules (often including p-phenylenediamine or related compounds) are mixed with a developer containing hydrogen peroxide. This mixture opens the cuticle, lightens natural pigment, and allows new colour molecules—formed through oxidation—to lock into the hair shaft for lasting results.

In the course of these reactions, additional compounds can form. Scientific literature has long examined the possibility that some of these reaction products may be irritating or sensitising to skin, and has explored whether long‑term exposure—especially for hairdressers who work with dyes daily—could be linked with certain cancers. Regulatory bodies have responded over decades by restricting or banning particular dye substances, capping concentrations, and requiring safety assessments under the UK’s Cosmetics Regulation (retained EU law). In practice, that means ingredients like PPD are allowed only up to set limits in the final mixed product and must carry clear usage and allergy‑test guidance.

None of this removes risk entirely—particularly for individuals already sensitised to PPD (for example, after a reaction to “black henna” temporary tattoos) or those with eczema or a history of allergic contact dermatitis. For these groups, even a correctly used, compliant dye may be problematic.

Who is most at risk — and early signs to watch

While anyone can react, certain factors increase risk:

• Previous reactions to hair dye or to temporary “black henna” tattoos (often contain high, unsafe levels of PPD).
• Existing skin conditions such as eczema, psoriasis, or very sensitive skin.
• Frequent colouring (short intervals between applications) or prolonged processing times beyond instructions.
• Poor ventilation during application, which can aggravate the eyes and airways.
• Occupational exposure for hair professionals handling colour multiple times daily without adequate protective measures.

Early warning signs of an adverse reaction may include itching, tingling, or burning on the scalp, forehead, ears, or neck; redness, rash, or blistering; swollen eyelids or face; streaming eyes; and wheezing or tightness in the chest. Severe symptoms can escalate quickly. If breathing becomes difficult, seek urgent medical help. For significant skin reactions, stop using the product immediately and consult a GP, pharmacist, or dermatologist.

How to colour more safely: practical, evidence‑based habits

There’s no zero‑risk cosmetic, but sensible measures can dramatically reduce the likelihood of problems:

• Patch test every time you colour, per the product’s instructions—typically 48 hours before. Sensitisation can develop over time, even if you’ve used a formula for years.
• Follow timing precisely. Do not exceed recommended development times or frequency. More time does not equal better coverage.
• Use gloves and ventilate well. Open windows or use an extractor; avoid inhaling fumes at close range.
• Avoid skin contact beyond the hairline. Use a barrier cream on the perimeter of your scalp and wipe any drips immediately.
• Never use hair dye on brows or lashes. This is explicitly warned against due to the risk of eye injury.
• If you’ve reacted before, stop and seek advice. A dermatologist can arrange patch testing to identify specific allergens.
• Consider alternatives: semi‑permanent deposit‑only colour, temporary root touch‑ups, or professional low‑odour and ammonia‑free services. Note: “ammonia‑free” does not automatically mean allergen‑free.
• For hair professionals: use gloves consistently, improve salon ventilation, rotate tasks where possible, and follow COSHH guidance for safe handling of chemicals.

During pregnancy, many choose to delay colouring in the first trimester as a precaution, though regulators consider approved products safe when used correctly. If you have concerns, speak with your midwife or GP and ensure excellent ventilation and minimal skin contact.

Industry and regulatory context in the UK

Under the UK’s retained EU Cosmetics Regulation, hair dyes are subject to safety assessments, concentration limits, and ingredient restrictions. Over the years, certain substances have been banned or tightly limited following scientific review, and product labelling must include allergy‑alert information and instructions for patch testing and safe use. The Scientific Committee on Consumer Safety (SCCS) has repeatedly evaluated hair dye substances, and guidance evolves when new data emerge.

For consumers, this means products on shelves have undergone review—but also that guidance matters. Labels are not optional reading. For professionals, it underscores the importance of personal protective equipment, training, and ventilation to reduce cumulative exposure. The discussion prompted by the latest report is part of a long‑running, iterative process of assessing risk and improving practice rather than a sudden change to the safety profile of hair dyes overnight.

Key Takeaways

• Permanent dyes use oxidative chemistry that can generate byproducts; most users colour safely, but reactions do occur.
• The three headline concerns are allergic dermatitis, respiratory irritation, and long‑term risks still being researched.
• UK‑regulated products are assessed for safety; always follow label directions and perform a patch test 48 hours beforehand.
• Improve ventilation, use gloves, avoid skin contact, and never use hair dye on brows or lashes.
• Those with past reactions or sensitive skin should seek medical advice; professionals should optimise PPE and ventilation.

Frequently Asked Questions

Are permanent hair dyes safe?
They are considered safe when used as directed under UK cosmetic laws, which limit concentrations and require safety assessments. However, no product is risk‑free. Allergic reactions and irritation can occur, especially in sensitised individuals.

What ingredient most often causes allergic reactions?
Allergic contact dermatitis is frequently linked to p-phenylenediamine (PPD) and related aromatic amines found in many oxidative dyes. If you’ve reacted before, avoid further use and consult a dermatologist for patch testing.

Do semi‑permanent dyes avoid these risks?
Semi‑permanent, deposit‑only dyes typically don’t use the same oxidative chemistry and may be better tolerated by some, but they can still cause reactions. Always patch test and follow instructions.

Can hair dye fumes affect breathing?
Yes, strong odours and vapours can irritate the eyes and airways, especially in poorly ventilated spaces. Open windows, use fans or extractors, and avoid leaning over the mixture as it develops.

Is there a cancer risk from hair dyes?
Research into long‑term risk is ongoing. Some studies of hair professionals show associations with certain cancers due to cumulative exposure. Evidence for personal home use is mixed. Regulators continue to review new data.

Should I colour my hair during pregnancy?
Many choose to delay until after the first trimester. If you proceed, minimise skin contact, ensure good ventilation, and follow instructions. If you’re unsure, speak to your midwife or GP.

What should I do if I develop a reaction?
Stop using the product immediately. For mild irritation, rinse thoroughly and seek pharmacy advice. For swelling, widespread rash, or breathing difficulty, seek urgent medical care.

How often is it safe to dye hair?
Follow the brand’s recommended intervals—typically 4–8 weeks. More frequent colouring may increase the chance of irritation or sensitisation.

Are “natural” or “ammonia‑free” dyes safer?
“Natural” is not a regulated term and ammonia‑free does not mean allergen‑free. Check ingredients, patch test, and treat all dyes with the same care.