How much topical emollient to apply?

Unlike the prescription of oral medications, the prescription of topical emollients is by its nature an inexact science. The amount of emollient that a person needs in order to gain maximum therapeutic benefit will depend on the extent of their dry skin (in terms of both the area affected and level of dryness) and their size, e.g. an adult will require more than a child and a large adult more than a smaller one. This means that judgements must be made by the health care professional as to the likely quantity required and clear instructions given to the patient to this effect. What is not acceptable is to expect the patient to follow a general instruction like ‘apply liberally’ as this may be interpreted in any number of ways.

Guidance for the correct amounts of emollients can be found in the British National Formulary (British Medical Association and Royal Pharmaceutical Society of Great Britain, 2007) and are laid out in Table 5.2. Other suggested quantities are provided by Britton who gives three possible regimes as guidance (Britton, 2003) (see Box 5.1). This is particularly helpful when explaining to patients as it may be easier for them to understand measures such as spoonfuls rather than grams or millilitres. Custom and practice has become that an adult with a dry skin condition should use around 500 g of topical emollient a week and a child should get through 250 g per week. This is only guidance and really only serves to ensure that patients with dry skin conditions are not prescribed quantities less than 500 g (unless it is for the convenience of having a smaller quantity to carry around.)

Table 5.2 Recommendation for quantities of emollients for an adult over a period of 2 weeks.     Creams and ointments (g) Lotions (ml)   Face 15–30 100 ml   Both hands 25–50 200 ml   Scalp 50–100 200 ml   Both arms or both legs 100–200 200 ml   Trunk 400 500 ml   Groins and genitalia 15–25 100 ml

Box 5.1 Amounts of emollient measured in spoonfuls A formal topical regime of emollient would be, for example, 10 g to each of the following areas: Each arm The chest The abdomen Each thigh Each shin Upper back Lower back 2 g to the face 10 g is the equivalent of a desert spoonful. If someone is less dry, the same ratios should be used by 5 g (a teaspoon) per area or 20 g (a tablespoon) per area if more dry.