Eczema sufferers - with their telltale angry-looking, scaly skin - are a familiar sight these days although, just a few decades ago, they would have been a small minority. Now, in most countries, about one in five children and one in 12 adults are living with some degree of this condition.
What has pushed eczema up the ranks to become one of the most common skin disorders of modern life? One short answer is the increasingly toxic environment in which we now live. We unwittingly expose ourselves to hundreds of chemical irritants and allergens - day in, day out. The sources of these toxins are often innocuous and ubiquitous to our current lifestyle - that bottle of washing-up liquid in the kitchen, that tube of toothpaste in your bathroom, that box of laundry detergent.
For atopic eczema sufferers who have an inherited allergic susceptibility, exposure to these chemicals aggravates their symptoms and perpetuates painful flare-ups. For those who weren't born with particular allergic tendencies, constant contact with toxic substances enables substantial amounts of chemicals to enter your system (the skin can absorb up to 60 per cent of whatever substances with which it comes into contact). These chemicals build up to the point where they push the immune system into toxic overload, triggering an eczema reaction. This type of eczema is called 'allergic contact eczema'.
Causal substances (or allergens) are not necessarily harsh or irritating, and don't provoke a reaction in everyone - only in those who have become sensitised to them.
The type of eczema that's not linked to an allergic reaction is known as 'irritant contact eczema'. Causal substances (or irritants) are often abrasive, and can cause inflammation in almost everyone if there is long- or strong-enough or frequent-enough contact.
Many eczema triggers have both allergenic and irritant properties. To find these toxic triggers, you need look no further than your own home. So, let's take a quick tour around your house and finger the usual chemical suspects.
Our first stop is the kitchen. Look under the sink and you'll find a veritable Pandora's box of chemicals among the cornucopia of household-cleaning products. Our obsession with removing dirt and making our homes germ-free regularly exposes us to a laundry list of skin irritants. One of these is sodium lauryl sulphate (SLS), frequently found in washing-up powders/liquids. It's a powerful foaming agent known for its effective degreasing ability - which is why it's also used in car washes and in garages to degrease car engines.
SLS concentrations as low as 0.5 per cent are already capable of causing irritation; higher concentrations of 10-30 per cent can cause skin corrosion, severe irritation and are even deemed dangerous (J Am Coll Toxicol, 1983; 2: 183-235). The powerful cleansing effect of this chemical dissolves and dries out the natural protective oils of your skin. It can also alter the quality of skin proteins (denaturation), which not only leads to skin irritation, but also makes the protective epidermal layer more permeable, thereby allowing easier access to other toxins to penetrate into the lower, more sensitive layers of the skin as well as to attack the immune system (Acta Dermatol Venereol, 1957; 37: 269-75).
Other common household-cleaner ingredients that are particularly corrosive to the skin and may trigger allergic reactions include:
* bacteria-killing disinfectants such as ammonia, chlorine and pine oil
* grease-cutting petrochemicals such as mineral spirits and phenol (or carbolic acid)
* stain-removing alkalis such as sodium or potassium hydroxide.
Even the water you use to wash your dishes and clothes could be making your eczema worse. UK researchers investigating eczema in schoolchildren found that it was significantly more prevalent in the hardest-water areas (Lancet, 1998; 352: 527-31). It is thought that the high calcium and magnesium content of hard water could either act as a skin irritant in itself, or interact with other chemicals to break down the skin's defences and allow the invasion of toxins.
And if you're thinking that a pair of rubber gloves could protect your skin from this chemical onslaught, think again.
Contact with rubber products is commonly associated with eczema. These flare-ups can be seen, with increasing prevalence, in healthcare workers who frequently wear tight-fitting latex gloves for hygienic reasons, as well as in atopic patients who have undergone multiple surgical operations (Rev Prat, 2002; 52: 1420-3). Eczema develops either as an allergic reaction to the natural latex proteins found in the material or as an adverse side-effect to irritant chemicals that have been added to the latex during manufacturing. Skin reactions to latex vary from the relatively mild (itching, slight redness) to the more serious (burning sensations, hives).
If you have to come into contact with chemical cleaners or products, you could substitute rubber gloves with ones made from vinyl or other non-latex materials.
Moving on from the kitchen sink, we can usually find cupboards packed with victuals and provisions to satisfy your family's appetite - as well as an arsenal of eczema-provoking allergens.
Intolerance to certain types of food has long been recognised to be a major cause of eczema - in particular, the atopic form. Common culprits include dairy, soy, eggs, wheat and shellfish. Avoiding these foods is easy enough once you've identified the ones to which you're allergic.
However, much of what we buy at the supermarket these days, even those claiming to have 'nutritional value', are chock-full of artificial flavours, preservatives and colours that worsen eczema. Food-allergy studies noted skin and/or intestinal reactions in people with atopic eczema to tartrazine dye, sodium benzoate and sodium metabisulphite preservatives (Clin Exp Allergy, 2001; 31: 265-73), and the flavour-enhancer monosodium glutamate (MSG) (J Allergy Clin Immunol, 1997; 99: 757-62).
Among these additives, tartrazine - alias E102 - is a particular menace. This synthetic orange-yellow colouring is considered one of the most aggressive allergens of all the azo dyes and, worryingly, it has infiltrated a vast number of food and beverages - such as coloured fizzy drinks, fruit squashes, cake mixes, custard powder, soups, sauces, ice cream, sweets, jam and mustard. It's also found in cough syrups and in the capsules containing medicines. Simply avoiding orange/yellow foods may not be enough as tartrazine is sometimes mixed with blue to produce various greens to enhance, for example, tinned peas.
Aside from eczema, other known reactions to tartrazine include migraine headaches, blurred vision, hyperactivity in children, and worsening of other atopic conditions often found with eczema such as asthma and a constant runny nose.
It's not only processed foods you need to watch out for. Whole, natural foods like fruit and vegetables are likely to sport a coat of pesticides that could spell trouble to hypersensitive people. A high prevalence of both allergic and irritant contact eczema has been found in rural populations and among agricultural workers (Sangyo Igaku, 1987; 29: 3-16; Dermatol Monatsschr, 1989; 175: 203-14).
What price beauty?
Onwards now to the bathroom where, scattered around the bathtub, we are likely to find a colourful abundance of bubble bath, shower gels and shampoos, each pledging to leave you squeaky clean and healthy.
Nevertheless, these products contain a cocktail of chemicals that threaten your health. You wouldn't dream of soaking yourself in a tub of washing-up liquid, but look more closely at your bottle of bubble bath and you'll find, lurking among the list of ingredients, SLS - that aggressive cleaning agent and common cause of eczema. Other bathroom hiding places of SLS are toothpastes, shampoos, shower gels and just about every personal-cleaning solution.
Most facial washes designed to keep your skin clear of unsightly spots use polyethylene glycol (PEG), a caustic that dissolves grease - whether on your person or in the oven. But it's also a recognised toxin that can cause an immediate or delayed allergic eczema reaction (Contact Dermatitis, 1978; 4: 135-8).
A relative of PEG, propylene glycol (PG) is a solvent used by manufacturers for its moisture-regulating, antiseptic and preservative effects. Commonly used in cosmetics, haircare products, deodorants and aftershave, it's also a main ingredient in antifreeze and brake fluid. PG is believed to be more irritant than allergen, and most skin reactions to the chemical tend to be due to its toxicity, rather than an allergic response (Contact Dermatitis, 1975; 1: 112-6; Hautarzt, 1982; 33: 12-4).
An allergen commonly found in cosmetics and toiletries is lanolin. To be more precise, it's the wool alcohols in refined lanolin that are often responsible for eczematous flare-ups. A natural product derived from fleece, lanolin's high fat content makes it a good moisturising base for products such as hand creams, skin moisturisers, glossy lipsticks, cream makeup foundation and bath oils. Ironically, it is used in some emollients to treat dry skin conditions such as mild eczema. Lanolin is also ubiquitous in hairsprays, air fresheners, household-cleaning products, laundry detergents, treated fabrics (for a waterproof finish) and clothes dye.
And what's a bubble bath if it doesn't exude the soothing aroma of ylang ylang or lavender? Fragrance has become a major selling point for many personal-hygiene products and cosmetics. But the cost of sweet-smelling skin is high, taking into account the more than 5000 chemicals used in fragrance manufacture - many of which are known toxins and allergens.
And if you've been using a favourite fragrance for some time now, you may want to consider drastically cutting down on that spritzing. Researchers have found a positive correlation between age and fragrance allergy. It appears that repeated exposure to fragrance and age-related susceptibility factors, such as increased skin permeability, both contribute to the increase in the number of fragrance-allergy sufferers (Br J Dermatol, 2003; 149: 986-9).
Other allergens and toxins that you submit yourself to in the name of beauty include:
* formaldehyde, commonly used as a preservative in cosmetics, as well as in cleaning agents and industrial products (Am J Contact Dermat, 1999; 10: 12-7)
* paraphenylenedeamine (PPDA) and related agents, found in permanent hair dyes and a common cause of occupational eczema among hairdressers (Contact Dermatitis, 2002; 46: 319- 24). Even home hair-dyeing kits, which mostly use semipermanent dyes, penetrate the shaft of the hair, allowing chemicals to enter the skin and cause an allergic reaction. Switch to temporary or vegetable (henna) dyes instead.
In the bedroom, let's head for the wardrobe full of clean, fresh-smelling clothes, courtesy of that tub of biological washing powder. This type of laundry detergent contains quantities of enzymes (proteases and lipases) that digest proteins and fats - for exceptional stain-removing even at low temperatures. But traces of these enzymes stay in the fabric and, when it comes in contact with the skin, can trigger eczematous reactions.
Switching to a non-biological washing powder may help, but those also contain irritants such as preservatives, to protect fabric against the effects of ageing, as well as synthetic fragrances, to give laundry that smell of 'summer freshness'.
The type of fabric is also important in controlling skin inflammation. Eczema sufferers are often told to steer clear of wool, an irritant even for those with normal skin sensitivity. But synthetic fibres also provoke or aggravate eczema. One study found that three synthetic shirts had a significantly greater capacity to irritate eczema patients, while a cotton shirt was the best tolerated (Z Hautkr, 1990; 65: 907-10).
What about that genuine leather jacket with the matching leather shoes you got for Christmas? They're made from a natural material and so should get a thumbs-up, right? Wrong - though it's not the leather that poses the problem, but the chemical used to treat it - namely, chromates, the chromium compounds used for tanning (Contact Dermatitis, 1996; 35: 83-5). Try substituting your leather items for those that have been vegetable-tanned instead. And when you're buying a new pair of shoes, it may be worth remembering that manufactured rubber shoe soles contain two common eczema allergens, thiuram and mercaptobenzothiazole (Allerg Immunol [Leipz], 1974-75; 20-21: 281-5).
Your jewellery box may also harbour allergens, especially if it contains nickel jewellery. Eczema on the ears is a familiar sight thanks to nickel-containing earrings. The metal is also used for belt buckles, zippers, buttons and snaps. Nickel-related eczema may be worsened by sweat as the moisture allows the metal ions to be better absorbed into the skin.
Less obvious sources of allergy are stainless-steel or chromium-cobalt products. Through chronic exposure from, for example, metallic orthopaedic implants, enough toxic metal can leach into the system and provoke an allergic eczema response (Rev Chir Orthop Reparatr Appar Mot, 1995; 81: 473-84).
This list of allergens and toxins, cleverly concealed in every corner of your home, is far from exhaustive. Our daily exposure to them has fuelled the rising numbers of eczema cases, and only by removing them can we control this epidemic.