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DermNet NZ


Facts about the skin from DermNet New Zealand Trust. Topic index: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


Emollients and moisturisers

What are emollients and moisturisers?

Emollients soften skin and moisturisers add moisture. They are used to correct dryness and scaling of the skin, fine lines and wrinkles and mild irritant contact dermatitis.

What are the causes of dry, scaly skin?

Dry, scaly skin may be due to:

How does dry skin arise?

Dry skin results from lack of water in the stratum corneum, the outer, compacted layer of non-living cells that covers the entire body like a layer of cling film. When it becomes dehydrated this layer loses its flexibility and becomes cracked and scaly. The stratum corneum contains natural water-holding substances that retain water seeping up from the deeper layers of the skin. Water is also retained in the stratum corneum by a surface film of natural oil (sebum) and broken-down skin cells, which slows down evaporation (trans-epidermal water loss or TEWL.)

Causes of dehydration of the skin

Water loss from the skin is increased by dry winter air, either outside on cold, frosty mornings, or inside in centrally-heated homes or offices. Wind also increases evaporation from the skin. Increasing age means the skin holds less water, particularly over the age of 50. People on diuretics for hypertension (high blood pressure) or heart failure, and those with underactive thyroid glands also have drier skins.

Another important factor in encouraging water loss from the skin is over bathing. Washing with hot water and soap washes off the surface layer of natural oil, which goes down the plug hole. Unless the oil is replaced with either an oil or an emollient applied to the skin after washing, water loss from the skin increases and an hour or so after bathing the skin is drier than it otherwise would have been. Detergents and solvents similarly encourage dehydration of the skin by removing the surface oil film.

How does scaly skin arise?

Scaly skin arises from visible detachment of cells from the surface of the stratum corneum. In normal skin this process is invisible because the scale consists of individual cells. In scaly skin the cells have difficulty in detaching from each other and come off in little ‘rafts’ which are easily visible. This occurs in dry skin from any cause but also in eczema, psoriasis and ichthyosis where the skin cells are imperfectly formed and don't detach properly.

Treatment of dry skin

To correct a dry skin tendency from any cause reduce contact with soap and water and apply a moisturiser or emollient.

Reduce bathing

Moisturisers and emollients

The terms ‘moisturiser’ (to add moisture) and ‘emollient‘ (to soften) are interchangeable as they describe different effects of these agents on the skin. Basically they have two actions:

Some moisturisers contain both occlusives and humectants.

Occlusive moisturisers

Occlusive emollients consist of oils of non-human origin, either in pure form or mixed with varying amounts of water through the action of an emulsifier to form a lotion or cream. A large variety are available, reflecting that there is no '‘right’ moisturiser for all patients: the most suitable one often having to be found by trial and error.

The choice of occlusive emollient depends upon the area of the body and the degree of dryness and scaling of the skin.

Sorbolene cream is a good all-round moderate-strength moisturiser that suits many patients because it is non-greasy, cheap and available in bulk without prescription.

250g (or ml) is a minimum quantity for an occlusive emollient and often 500g or 1Kg is needed: liberal and regular usage is to be encouraged. How frequently it is applied depends on how dry the skin is: very dry skin may benefit from a greasy emollient every couple of hours, but a light moisturiser may only be needed on slightly dry skin at night.

Humectants

Humectants, agents adding water to the stratum corneum, include:

Urea and lactic acid preparations often sting if applied to broken (scratched or cracked) skin. Humectant / keratolytics are particularly important in management of the ichthyoses (inherited or acquired scaly disorders of the skin).

Adverse Reactions to emollients

Other treatments for scaly skin

Emollients are always an important part of treatment for scaly disorders such as eczema, psoriasis and the ichthyoses. However, other agents are often needed to normalise skin cell formation and correct the scaling. These include:

Related information

References

On DermNet NZ:

Other websites

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Author: Mark Duffill MBChB(NZ) FRCP(Ed) Dip Derm(Lond)
Department of Dermatology, Health Waikato.

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If you have any concerns with your skin or its treatment, see a dermatologist for advice.