Greys peeping through or want a bold new look? Before reaching for the hair dye, check for any nasties on the label. Millions of us regularly colour our hair, whether that’s with an at-home kit or at the hairdressers.
However, certain chemicals in dyes are irritants or could be bad for your body – in some cases provoking severe allergic reactions – so it’s a good idea to know what you’re putting on your scalp.
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What chemicals should I look for?
There are dozens of ingredients that help hair dye work its magic. But there are some potentially harmful chemicals that are quite common in hair dye.
The most common culprit that people react to is PPD, or p-Phenylenediamine, found in darker shades. Symptoms vary from dermatitis (itchy, red skin), to, in rare instances, life-threatening anaphylaxis.1
PPD is often used in black ‘henna’ tattoos instead of the natural ingredient. The NHS warns levels of PPD in this dye could be toxic, so these tattoos are best avoided.2 If you have had a black henna tattoo in the past you may increase your risk of allergy to PPD. If you have reacted to black henna or PPD containing hair dyes before it is best to avoid dyeing your hair. However, hair dyes containing PPD should be safe as long as you follow the safety instructions, including a patch test (see below).
You probably learned about this colourless, alkaline gas in chemistry lessons at school. It’s used in colourants as it opens up cuticles – a hair’s scaly outer coating – allowing the colour to penetrate. But over time, ammonia can leave tresses dry and brittle.3
In strong concentrations, ammonia causes severe burning. But even in low concentrations, like those in hair dye, it can irritate skin, lungs or eyes if you’re sensitive.
This is widely used in hair dye as it removes hair’s pigment, allowing new colours to be absorbed, from chestnut brown to hot pink.4
Concentrated hydrogen peroxide is nasty stuff – it’s toxic if ingested or inhaled, and causes tissue damage if it comes in contact with skin or eyes.5
Even at the low levels used in hair dye, repeated use can leave hair parched and lacklustre. A study published in the Journal of Dermatology found exposure to hydrogen peroxide left hair weaker.6
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Used as a colour additive for years, this works by combining with protein in hair to gradually darken your barnet over time.7 These days it’s banned in Europe, with calls to ban it in the US too.8
This is because lead is poisonous, causing serious health problems even in small amounts.9 However, trials by the US Food and Drug Administration found lead wasn’t absorbed into the bodies of those using lead acetate-containing hair dyes.10
How to be colour-safe
Always conduct a skin patch test at least 48 hours before using dye to check you’re not allergic, even if you’ve used that colourant before.11 If you’re visiting the hairdressers, request a patch test at least two days before your appointment.
If you’re dying your hair at home, follow the instructions on the packet for a patch test. Monitor your skin and health carefully; if you develop any redness, itchiness or burning, or you start to feel poorly, avoid using the hair dye.12
Even if your skin doesn’t react, avoid prolonged contact with hair dye chemicals; wear gloves while applying the dye, don’t leave it on your head longer than recommended, and thoroughly rinse it off.
What can I use instead?
If you think that you are allergic to PPD it is recommended that visit your doctor to be referred to an allergy clinic13.
You could switch to natural dyes such as henna, derived from the Lawsonia inermis plant, which has been used for centuries as a natural hair dye in countries like India.14 Or switch to semi-permanent hair dyes. Take care though – if you are switching to semi-permanent, consider avoiding Para-toluenediamine sulfate (also known as PTDS) as 40% of PPD allergy suffers also reacted to this dye.
If you think that you are reacting to the harsh chemicals/irritants in the hair dye such as ammonia switch to vegetable-based dyes that are free from ammonia and other additives.
Don’t forget your patch test though, as you can still react to natural ingredients.
Advice is for information only and should not replace medical care. Please check with your GP before trying any remedies.
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- Hair dye reactions. Available from: www.nhs.uk/conditions/hair-dye-reactions/
- As above
- Gavazzoni Dias MR. Hair Cosmetics: An Overview. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4387693/
- Compound Interest. The Chemistry of Permanent Hair Dyes. Available from:http://www.compoundchem.com/2015/05/14/hair-dyes/
- Watt BE, Proudfoot AT, Vale JA. Hydrogen peroxide poisoning. Available from: ncbi.nlm.nih.gov/pubmed/15298493
- Jeong MS, et al. Significant damage of the skin and hair following hair bleaching. Available from: www.ncbi.nlm.nih.gov/pubmed/20860738
- Aparacida da Franca S, et al. Types of Hair Dye and Their Mechanisms of Action. Available from: http://www.mdpi.com/2079-9284/2/2/110/htm
- Chemical Watch. US FDA petitioned to prohibit lead acetate in hair dye. Available from: https://chemicalwatch.com/53894/us-fda-petitioned-to-prohibit-lead-acetate-in-hair-dye
- World Health Organization. Lead poisoning and health. Available from: www.who.int/mediacentre/factsheets/fs379/en/
- US Food and Drug Administration. Lead acetate in ‘progressive’ hair dye products. Available from: www.fda.gov/Cosmetics/ProductsIngredients/Products/ucm143075.htm
- As Source 1
- As Source 1
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- Semwal RB, et al. Lawsonia inermis L. (henna): Ethnobotanical, phytochemical and pharmacological aspects. Available from: https://www.sciencedirect.com/science/article/pii/S0378874114004115