Topical corticosteroids are also split into four classes of potency and measured in finger tip units (FTUs).
Potency
The potency of a medication is a measurement of how powerful the effect of the medication will be.
The four classes of potency for topical corticosteroids are:
- mild topical corticosteroids, such as hydrocortisone; used to treat mild cases of skin inflammation, such as insect bites or contact dermatitis
- moderate topical corticosteroids, such as clobetasone butyrate; they treat more troublesome skin conditions, such as atopic eczema or severe cases of nappy rash
- potent topical corticosteroids, such as betamethasone dipropionate; used to treat skin conditions, such as psoriasis or seborrhoeic dermatitis, which do not respond to other treatments
- very potent topical corticosteroids, such as clobetasol propionate; used on a short-term basis to treat severe ‘flare-ups’ of symptoms that do not respond to other treatments
To reduce the risk of side effects, your GP will prescribe the least potent corticosteroid necessary to relieve your symptoms.
Finger tips units
An FTU is the amount of topical corticosteroid needed to squeeze a line from the tip of an adult finger to the first crease of the finger.
An FTU is about 500mg. It should be enough to treat an area of skin double the size of the flat of your hand with your fingers together.
The recommended dosage in terms of FTUs will depend on what part of the body is being treated. This is because the skin is thinner in certain parts of the body and more sensitive to the effects of corticosteroids.
For adults, the recommended FTUs to be applied in one single dose are:
- 0.5 FTU for genitalia
- 1 FTU for hands, elbows and knees
- 1.5 FTUs for the feet, including the soles
- 2.5 FTUs for the face and neck
- 3 FTUs for the scalp
- 4 FTUs for the hands, arms and buttocks
- 8 FTUs for the legs and trunk (the main section of the body, excluding the arms, legs and head)
For children, the recommended FTUs will depend on their age. Your GP can advise you about this.
Frequency
For most conditions, you will only need to apply topical corticosteroids once or twice a day.
Length of treatment
The recommended length of treatment will depend on the condition being treated and the strength of the topical corticosteroid being used.
Mild to moderate topical corticosteroids can usually be used indefinitely to treat chronic (long-term) skin conditions, such as atopic eczema. However, most people only need treatment when they have a flare-up of symptoms. They will not need to use a topical corticosteroid every day.
Potent and very potent topical corticosteroids are often prescribed for a shorter period of time. If treatment is required for a long period of time, it is likely you will be referred to a dermatologist (skin care specialist).
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