It is estimated that the average adult uses at least seven different skin care products each day, so it’s not surprising that reactions to these products are very common. Reactions can be seen after the first application or after years of use. In New Zealand, like the rest of the developed world, there is a trend towards using "natural products", with the misconception that natural products are "healthier" and cause fewer reactions than artificial products. This myth is debunked when people are reminded that most allergens are "natural” proteins.
What is even more worrying is the fact that there are at present no regulations in New Zealand that cover cosmetic ingredient labelling. In October 1991, the Cosmetic Ingredient Labelling Regulations were introduced in Australia. These regulations define the term “cosmetic product” and require that all ingredients be listed in descending order of concentration (although no naming convention is specified nor is there a minimum print size requirement apart from it being legible). This is a major step in helping consumers become aware of exactly what they are rubbing into their skin and putting in their hair. In New Zealand it is still possible to buy cosmetics with no proper labelling, with known allergens omitted from the label or with the term "hypoallergenic" used loosely on the label.
Problems associated with cosmetics and skin care products• Contact dermatitis
• Urticaria (hives)
Let’s look at each of these conditions in detail.
Contact dermatitisContact dermatitis is simply inflammation that results from the interaction of skin and a substance (even water) that comes in contact with it. For the vast majority of people, these substances are harmless. Contact dermatitis can look - and itch - very much like eczema. It usually presents as a rash of tiny blisters, inflamed reddened skin, sometimes dry, or sometimes moist and oozing.
Contact dermatitis is produced through one of two major pathways: irritant or allergic. Irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD) are two of the most common dermatologic conditions in industrialised societies, with a prevalence of up to 10 per cent. The two conditions are clinically indistinguishable and often both conditions co-exist. Many of the allergens causing ACD are also irritants.
Irritant contact dermatitisIrritant contact dermatitis predominates, accounting for 80 per cent of all cases of contact dermatitis. ICD is a non-immunologic skin reaction that does not involve immune system sensitisation (previous exposure to the allergen). It can occur in all members of the population depending on the "irritancy" of the chemical, the duration of contact and individual susceptibility. Atopics (who invariably have dry skin) are more prone to irritant dermatitis. Water is one of the most common irritants; therefore atopics who do a lot of wet work will often get irritant hand dermatitis. Another reason atopics get irritant dermatitis is that the skin gets injured from chronic scratching, allowing the otherwise harmless chemicals in cosmetics to enter the skin. The most common skin irritants include acids, alkalies, detergents, and solvents that disrupt the barrier function of the skin. Common skin care products causing skin irritation include bath soaps, make-up removers, shampoos, antiperspirants, and permanent hair-waving solutions. Water present in cosmetics and skin care products is the most common irritant to very dry skin.
Allergic contact dermatitisAllergic contact dermatitis, on the other hand, is an immunologic skin reaction that occurs in a genetically predisposed individual. The allergic response occurs only when a person’s immune system is sensitised to the allergen. This reaction is also known as delayed hypersensitivity reaction, since the rash usually develops more than 12 hours after contact with the allergen. The number of chemicals known to be capable of causing ACD is said to be near 3000 and constantly increasing.
Common allergens in cosmetics and skin care products that cause contact dermatitisThe most common allergen causing ACD is fragrance. More than 5000 different fragrances are used in cosmetics and skin care products. Seventy to eighty percent of fragrance allergy can be picked up by patch testing with Balsam of Peru and Fragrance Mix (which contains 8 common fragrances). Fragrance can also cause increased pigmentation of the affected skin, photodermatitis or contact urticaria.
It is important to know that "unscented" does not mean "fragrance-free". Some unscented products may contain a fragrance to mask other chemical odours. To indicate that no fragrance is added to a product it must be marked "fragrance-free" or "without perfume". Other common sensitisers (contact allergens) include preservatives, lanoline, p-phenyldiamine (dye) and an increasing number of herbal (plant) products.
Preservatives in cosmetics and skin care products are the second most common cause of skin reactions. Cosmetics that contain water must contain some preservative to prevent bacterial or fungal growth.
Examples of cosmetics preservatives include:• Parabens
• Imidazolidinyl urea
• DMDM hydantoin
Common herbal products causing contact dermatitis include plants from the Compositae family:
• Daisy (Chrysanthenum)
• Dandelion (Taraxacum)
• Ragweed (Ambrosia)
Several plants in the Compositae plant family are regularly included in "natural skin care products" in New Zealand, especially shampoos and aromatherapy solutions. In some cases the reactions to Compositae is worsened by sunlight, often giving the appearance of a light-sensitive rash.
PhotosensitivityPhotosensitivity is the term used to describe skin disease caused by the interaction of UV radiation and an exogenously (externally) acquired chemical agent, which may be either a drug or food taken orally, or a substance applied to the skin. It can be divided into photodermatitis, also referred to as photoallergic dermatitis, and photoirritant contact dermatitis.
Plants that cause photodermatitis (Phytophotodermatitis)Phytophotodermatitis produces reddening and blisters on first exposure followed by persistent hyperpigmentation (darkening of the skin). This darkening of the skin can last for months. The rash is produced via a phototoxic reaction, which simply means that the reaction renders the skin susceptible to damage by UV light, and symptoms include burning pain at the affected site. This is in contrast to the reaction produced by plants such as poison ivy, which is classified as allergic contact dermatitis, and involves symptoms such as intense itching.
Compounds related to furocouramins (psoralens) usually cause plant-related photosensitivity. Two requisites for initiation of phytophotodermatitis are contact with a sensitising plant (eg. furocouramin) and exposure to ultraviolet light (wavelength greater than 320 nm), usually sunlight. Therefore, this dermatitis is usually seasonal.
Common plants causing photodermatitis:
In New Zealand many of these plants are also being added to "natural skin care products".
Contact urticaria is a hives-like reaction occurring at the site of contact of the skin product and usually occurring within 15 minutes of the product touching the skin.
Diagnosis of skin rashes caused by cosmeticsContact Urticaria is diagnosed by applying the product to the skin for 15 - 20 minutes and observing the skin for redness, swelling and itching.
Contact Dermatitis is diagnosed by doing a patch test. The only way to obtain proof of allergic contact dermatitis is by patch testing. This is different from skin prick testing (which gives a positive response in 15 minutes) in that it is a delayed hypersensitivity response (it gives a positive response in about 48 hours).
Chemicals are taped to the back in small chambers. The skin is not broken. The patches stay in place for 48 hours. You cannot shower or do any work or exercise that will wet or loosen the patches.
After two days, the patches are removed, and a reading is done. The patch sites are marked, and you may be asked to return for a final reading on another day. An experienced doctor can differentiate between allergic contact dermatitis and an irritant reaction on patch testing.
Photo-patch testing is patch testing with the addition of radiation to induce the formation of photoantigens. All photosensitive patients should be photo-patch tested.
In a recent study in Portland, Oregan, USA, 63 per cent of patients with suspected cosmetics dermatitis that had used a skin product containing botanical extracts were patch test positive to a botanical extract. In New Zealand the true prevalence of contact allergy to botanical extracts in patients with cosmetics dermatitis is unknown, as most people who suffer from skin rashes do not seek medical help.
By Dr Vincent St Aubyn Crump, Auckland Allergy Clinic www.allergyclinic.co.nz