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Last Updated: Wednesday, 13 June 2007, 10:51 GMT 11:51 UK
Harsh soaps blamed for allergies
The skin may be damaged by harsh cleaning products
Excessive washing with harsh soaps and abrasive skin care products is being blamed for a rise in allergic diseases such as eczema.

The "hygiene hypothesis" pins the rise on people being too clean, resulting in the immune system becoming too sensitive to infection.

But University College London's Institute of Child Health believe there could be a more direct cause.

They believe over-use of harsh products strips away a protective layer of skin.

Despite its popularity over the past 20 years there is very little supporting evidence for the "hygiene hypothesis"
Professor Robin Callard

This, they write in the journal Trends in Immunology, could make people more vulnerable to an allergic disease.

Rates of eczema and other allergic diseases are rising across the developed world.

Researcher Professor Robin Callard said many strong soaps, exfoliant beauty products and biological washing powders were all potent enough to strip away the skin's protective outer layer.

His research has shown that this protective layer is weakened in people with a rare genetic skin disease who develop eczema or other allergies.

Penetrating the skin

The UCL team has also shown that if the outer protective layer of skin is stripped away - using something as simple as sellotape - allergy-causing particles are able to penetrate the skin.

They are then taken up by specialised cells called Langerhans cells, which are found in a layer of the skin called the epidermis.

The Langerhans cells then move from the skin to the local lymph nodes of the immune system, and induce an allergic response.

Professor Callard said: "Despite its popularity over the past 20 years there is very little supporting evidence for the "hygiene hypothesis".

"In contrast, there is mounting evidence from both studies of rare genetic conditions and our lab work to support an important role for abnormalities in the outer protective layer of the skin in allowing allergic sensitization."

Professor John Harper, who also worked on the study, said people had nothing to fear from normal standards of hygiene - the potential problem was over-zealous use of harsh cleaning products.

He said: "Good standards of hygiene are clearly important to prevent spreading of unpleasant diseases.

"But if this proposed mechanism does turn out to be true, we may be able to reduce the incidence of these diseases by developing new treatments which specifically target the outer protective layer of the skin."

Margaret Cox, of the National Eczema Society, said: "Patients with atopic eczema have especially sensitive skin.

"Because soap and biological detergents de-grease the skin, if you are genetically predisposed to eczema you would be well advised to avoid using such products and switch to less abrasive and more nourishing emollients."

Over the last 30 years the prevalence of eczema in the UK has increased three fold.

09 Mar 06 |  Medical notes

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