Dog shampoos and hand allergy – watch out!

November 11, 2019 / Duncan Fisher
A recent paper draws attention to this still unregulated hazard.

Legislation in most countries protects us from exposure to known allergens in our skin and hair products, such as might be used as preservatives or fragrances.

This is not true of products we use on our pets.

Perhaps unsurprisingly, then, our pet products very often contain ingredients that are known to elicit allergic reactions in humans.

This is the substance of a paper1 presented last July before the annual meeting of the British Association of Dermatologists. This paper summarized results of a systematic survey of cosmetic products intended for use on dogs, all available on the shelves of UK pet stores and garden centers as of December 2018.

62 products were surveyed, 27 of which were of the leave-on variety, for detangling and deodorizing, and 35 were rinse-off shampoos or conditioners. The investigators simply searched the labelling for known allergens.

The results? Not good.

40% of these pet care products contained methylisothiazolinone (MI) and/or methylchloroisothiazolinone (MCI), labelled together sometimes only as ‘Kathon CG’. Worryingly – but entirely consistent with regulations – a further 11% were labelled only as containing a ‘preservative blend’, or had no ingredient listing at all. 40% is therefore a conservative number.

What are MI and MCI?

MI is a preservative, used originally in paints, glues, and cleaning agents. It has been found to be a very strong allergen, responsible for what American physicians are calling an 'epidemic' of contact allergic dermatitis. One physicians’ group named it Contact Allergen of the Year in 2013.

MCI, another preservative, is actually a very well known chemical allergen. In high concentrations it can even burn. It has long been removed from most human cosmetics, and now only appears in rinse-off products, in very low concentrations.

Both of these preservatives still exist in abundance in pet care products.

One more product surveyed contained methyldibromoglutaronitrile (or MDBGN). This is another kind of cosmetic preservative, a bromine-containing one, that turns out to cause problems in particular for eczema patients. The United States and the EU have largely banned its use now, and over the last ten years sensitization rates to it have been dropping steadily.

Preservatives aren’t the only problem in animal care products. 71% of the surveyed potions also contained ‘fragrance’, mostly unspecified, but some of the time named as hydroxyisohexyl cyclohexene carboxaldehyde, known commercially as ‘Lyral’. Lyral is already so well known as an allergen that the European Union has just decided to ban it completely – in human preparations, anyway.

Preservatives and fragrances remain largely unregulated in animal care products, however. Washing your dog, in other words, particularly if you have any tendency toward allergy, can cause you problems.

Know what you’re using, and make sure your doctor knows

We’ve written before about what allergy is. It’s not simple irritation. Nor is it an intolerance. It’s more complicated than either of these. Allergies, strictly defined, are when the immune system mistakenly produces antibodies against a foreign substance. (That foreign substance, supposedly harmless, is what we mean by ‘allergen’.) Allergy is an immune response, often a very complex one.

It takes a doctor, sometimes an immunologist, to know whether you’ve got a true allergy. But if you’re caring for an animal, and you’ve developed an irritant rash, particularly on your hands, it’s well worth telling your dermatologist. You can bring the bottle with you, to show the label. You may very well have developed an allergy, and there are things to be done about it. (Allergy can be treated.) The first of these things, needless to say, will be to stop using that product.

1 L. Howard, N. Mansoor and D.A. Buckley, ‘Dogs: a hidden source of exposure to common allergens’, Paper presented at Annual Meeting of the British Association of Dermatologists’, Liverpool, July 2nd – 4th 2019.

Questions about your skin? Ask our dermatologists online for $35.