Toxicologist David Basketter says that the rise in allergic reactions to a chemical widely used in hair and beauty products is unprecedented.
David Basketter is an authority on the identification and assessment of chemicals that can cause skin irritation and allergic reactions. He says that the rise in skin allergy cases caused by exposure to a widely-used chemical preservative is “the most alarming I’ve seen.”
The preservative has a long and complicated name – methylisothiazolinone (known as MI) but its use is a simple one. It’s included in many water-based cosmetic products to help prevent bacteria and yeast growing in the product, so extending the product’s shelf life.
For many years, MI was used in combination with another, very similar chemical called methylchlorolisothiazolinone (known as MCI) – and together they’ve been effective and relatively safe when used at a concentration of up to 15 parts per million (ppm).
But with only a limited number of effective preservatives available, and with demand increasing, manufacturers have been using MI on its own, and at an increased concentration of up to 100 ppm. These changes in use of MI could well be causing the problem.
At a meeting of the British Association of Dermatologists, the presence of MI and MCI in personal care products was reported as causing most concern – for instance in moist tissue wipes, cleansers, shower gels, deodorants and shaving foam. And the BBC’s ‘Watchdog’ programme recently highlighted increasing concerns about the use of MI.
It’s long been known that MI has the potential to cause allergic reactions, which is why it could only be used in limited concentrations. But it now seems that the danger was underestimated.
David Basketter says: “To give some perspective, we’d expect ‘safe’ preservatives to generate a reaction in 0.1 to 1.0% of eczema patients tested. Often, these are not so effective at preservation. Some more effective preservatives might produce a response in 1-2% of patients, which is regarded as unfortunate, but just about acceptable. But clinics all over Europe are reporting rapidly rising rates of allergic responses, and we’re seeing 5% or more of responses in testing. This is unprecedented and unacceptable.”
And the problem is even more worrying because the risk of skin allergy normally comes from products that stay on the skin like moisturisers and deodorants. Now dermatologists are reporting reactions to MI used in rinse-off products – like shampoos and conditioners – as well.
MI seems to be causing more problems than hair dye chemicals like PPD and PTD, and setting agents like ammonium thioglycate. “I strongly advise salon professionals to be alert to the dangers of MI both to their clients and themselves,” David Basketter advises, “we know that MI used in combination with MCI has several years of safe use. But where you see MI used on its own, beware!”
Chris Flower, Director General of the Cosmetics Perfumery & Toiletry Association has commented that the use of MI and MCI is a complex issue and that the cosmetics industry should work in partnership with dermatologists and the broader scientific community to address the issue: “Dermatologists have reported a high level of allergies to MI amongst patients in their clinics and industry is taking this information seriously. We should remember that the majority of people will not develop an allergy to MI from cosmetic products; it is not in their genes to be susceptible. Even though the actual number of people in the public at large with an allergy to MI is small, each one is important to us and it is a matter of great importance that we – the cosmetics industry, dermatologists and regulatory authorities – take the most appropriate action in a timely manner.”