Going further, dermocosmetics in atopic dermatitis management: hygiene products and emollients

Atopic dermatitis is a chronic inflammatory skin disease characterized by a tendency towards dry skin on which eczema patches develop.

It is known that:

• Atopic dermatitis is more prevalent in developed countries than in developing countries
• The prevalence in migrants leaving a developing country (e.g. Africa or the West Indies) to settle in a developed country (e.g. the UK) equals or exceeds that of the indigenous population after a few years
• The prevalence has been steadily increasing for forty years

These observations suggest that several environmental factors are involved in the expression of atopic dermatitis, including microbial factors and factors maintaining or aggravating dry skin.

Management includes two complementary aspects: treatment of eczema flares and dry skin management.
Dermocosmetics (hygiene products and emollients) have an essential role because of barrier function anomalies, which appear to be the primum movens of the disease.

Hygiene products in atopic subjects

Syndet soaps have now surpassed conventional soaps.
The chemistry of these products is complex: the washing and cleansing properties are due to the presence of amphiphilic molecules called surfactants¹. These are formed with a hydrophilic moiety (head) and a hydrophobic apolar moiety (tail). In aqueous media, they form soluble micelles that carry lipid fragments and other debris present on the skin surface.

There are two types of amphiphilic molecules: some are natural (fatty acids of plant origin, such as olive, palm, laurel or coconut oil). These are commonly referred to as soaps. Others are derived from petroleum chemicals (synthetic detergents or syndets). These are long-chain fatty acids with a highly variable composition. They are generally classified according to their polarity.

Most syndets consist of a combination of these different surfactants. They enhance the formulation by providing benefits in terms of texture, foaming power, solubility and rinsing properties. The ‘soap-free’ label simply means that the product does not contain salts of plant fatty acids (e.g. olive or laurel oil), i.e. only synthetic fatty acids (petroleum extract).

What about the long-term safety of these products?

Syndets have the same chemical structure as natural soaps — they are amphiphilic. They cleanse the skin and so are somewhat aggressive since they alter the barrier function by solubilizing lipids of the horny layer.

Anionic forms have the same characteristics as natural soap. They have a negatively charged head. They are present in most personal care products and act on the skin surface through two properties:

• By reducing the surface tension and energy. As the surfactant lowers them, the cleansing properties increase and it emulsifies fatty acids to a greater extent (by enclosing them in surface debris);
  
• By their ability to spread over the surface (i.e. wettability). As they increase, the contact angle becomes small to nil, while the cleansing properties increase because they spread more. In return, they solubilize a portion of membrane lipids (especially ceramides) and induce corneocyte cytolysis. They denature keratin and cell membrane and collagen fibre turgor. Several studies have shown that the tolerance of syndets depends on their composition.

Emollients in atopic subjects

The purpose of applying emollients in atopic dermatitis is to improve skin dryness, reduce itching and limit flares². This is an essential part of the treatment.

Guidelines for emollient application

Proposals have been put forward for the standardization of atopic dermatitis management in France (SFD, 2005) and for the use of emollients in England (BAD, 2013).

It is essential to first explain to the patient and his/her family:

• The common causes of atopic dermatitis and the importance of treating dryness
• The natural history of atopic dermatitis and its various stages
• The difference between eczematous patches (requiring topical corticosteroid or immunosuppressant therapy) and dry skin (requiring emollient application)
• The application of emollients should reduce the number of flares and the need for topical corticosteroid therapy
• The advantages of prescribing two types of emollient to tailor applications to the site (face, folds, limbs), the importance of considering the extent of dry skin, the time of flares and planned activities (difficulty of wearing clothes over areas treated with oily products)
• The importance of using a sufficient quantity of emollients for regular daily massage (to penetrate the products).

Applications should be tailored to seasonal variations and the severity of the disorder and flares, while considering the cost of the products and especially prescribing high volumes.
Unsuitable cleansing products containing detergents (and sometimes even sodium lauryl sulfate) should be avoided. They could contribute to altering the barrier function and should never be used to excess.
The onset of tingling or burning in areas where emollients have been applied could reflect sensitization to one of the components (e.g. a plant extract) or an underlying eczema exacerbation requiring the discontinuation of emollients and topical corticosteroid applications for a few days.

Conclusion

Impaired skin barrier function and severe dryness are major factors in the physiopathology of atopic dermatitis. Managing these disorders may reduce the intensity and number of flares and enhance patients’ quality of life.

There are two additional gestures: adopt good daily hygiene and regularly apply emollient care formulated for atopic skin.

It is essential to moderate hygiene habits, i.e. avoiding excessive hygiene which promotes skin dryness, itching and maintains eczema.

Emollients are necessary. They have been established as essential adjuvants for successful atopic dermatitis management. Detailed instructions on their use are required.

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