Most patients with chronic plaque psoriasis have a mild form of the disease that can be managed in a primary care setting using topical treatments, and this is the first-line treatment option. Successful treatment depends on good adherence and correct application of products. Topical treatment options include emollients, topical corticosteroids, vitamin D analogues, coal tar and dithranol.

Patients usually need different products for three areas of the body €“ trunk and limbs, face and flexures (where the skin is thinner) and the scalp. The NICE guideline recommends that treatments should be tried in a logical sequence until satisfactory products are found. Should there be an unsatisfactory response at any stage, it is important to check whether there have been difficulties with application, cosmetic acceptability or tolerability before changing to a different treatment.

If problems have prevented effective use of a treatment, it may be possible to offer an alternative formulation. Patients should be offered a supply of their treatment to keep at home for selfmanagement of the condition.

Emollients

All patients with psoriasis should be encouraged to use an emollient regularly. Emollients restore pliability to the skin and reduce the shedding of skin scales, which patients find embarrassing. They can also reduce pruritus (itching) and help prevent painful cracking of the skin as well as bleeding.

Patients should be encouraged to experiment with emollients until they find products that suit them. Emollients that contain humectants (e.g. urea or glycerin) are generally more effective moisturisers and have longer-lasting effects. Suitable products include Eucerin Dry Skin Intensive 10% Urea Treatment Cream, Hydromol Intensive and Neutrogena Dermatological. An emollient bath additive can also be used to counteract the drying affects of bathing.

Corticosteroids

Topical corticosteroids do not smell, stain or cause irritation and are often effective for controlling flare-ups. However, these advantages have to be balanced against the risks of local side effects such as skin thinning, the risk of rebound psoriasis after discontinuation and the risk of systemic side effects.

In order to minimise the risk of side effects, there should be a four-week break between courses of treatment with potent or very potent corticosteroids. Vitamin D or coal tar products may be used during this time.

Vitamin D

Vitamin D and vitamin D analogues normalise skin cell behaviour in psoriatic plaques and can clear psoriasis in six to eight weeks. The most effective way to use them is in combination with a topical potent corticosteroid (current first-line treatment).

Vitamin D products do not smell or stain like tar and dithranol. Nor do they carry the risk of the skin thinning, which is seen with topical steroids.

Tar preparations

Coal tar has been used in the treatment of psoriasis for decades. It is believed to be keratolytic, with some antiinflammatory and antiproliferative effects. In addition to proprietary preparations, crude coal tar, one to five per cent in white or yellow soft paraffin or emulsifying ointment has been used.

Crude coal tar stains clothing and smells unpleasant to many people. In addition, it is less effective than vitamin D derivatives. Coal tar is present in a number of OTC products.

Dithranol

Dithranol has been used for the treatment of psoriasis for many years. It is believed to exert a direct anti-proliferative effect on epidermal keratinocytes. It is profoundly irritant to normal skin, causing inflammation and severe blistering.

It causes a purplebrown temporary staining of skin and also stains clothing and bathroom fittings permanently. For many years, dithranol has been incorporated into Lassar's paste (zinc and salicylic acid paste BP) so that it can be applied to psoriasis plaques and kept away from uninvolved skin. This is made in concentrations from 0.1 per cent up to two per cent and the concentration used is gradually increased according to the patient's response.

In recent years, shortcontact dithranol treatment (SCDT) has been used, which involves application of dithranol in concentrations of up to eight per cent for between 15 and 30 minutes, with or without UVB irradiation. For some patients, SCDT is suitable for home use. A response can be expected within 20 days, but care must be taken to avoid contact with normal skin and facial skin.

Dithranol treatment is impractical if there are multiple small plaques and it is not suitable for the treatment of flexural psoriasis because of its irritant nature.