Eczema, pruritus, dry skin conditions
Emollients can be added to the bath or used in the shower and are especially useful in atopic eczema and ichthyoses. Some may also be used as substitutes for soap. They are used to smooth the surface of the skin and to increase its degree of hydration. They act either by occluding water loss from the outer layer of skin, eg white soft paraffin, greasy emollients, emulsions and sprays, or by improving the binding of water to the skin, eg urea creams. Some patients experience a stinging sensation after application of creams containing urea and also find their odour unpleasant. Stinging is reduced if preparations are applied to moist skin. Lanolin-containing creams can cause allergic sensitisation unless rendered hypoallergenic by purification. Large quantities of paraffin-based preparations may pose a fire hazard; patients should be advised to regularly change clothing, bedding and dressings impregnated with such products and keep away from naked flames.
In infected eczema, emollients containing antibacterial agents such as benzalkonium chloride are effective against the causative bacterium Staphylococcus aureus.
The immunomodulators tacrolimus and pimecrolimus applied topically have been successful in the treatment of eczema. Unlike steroids they can be applied to delicate areas such as the face and neck and they do not cause the side effects commonly associated with topical steroids. Dupilumab is a monoclonal antibody given by subcutaneous injection to treat moderate to severe atopic dermatitis. For topical steroids used in eczema see the inflammatory skin conditions section in this chapter.
The retinoid alitretinoin has been shown to produce a clinical response in severe hand eczema unresponsive to treatment with potent topical steroids. Due to its teratogenic potential, alitretinoin must not be given to pregnant women and if using to treat women of childbearing potential there should be strict measures in place to ensure that pregnancy does not occur. Alitretinoin should not be prescribed if a patient's eczema can be adequately controlled with standard measures, including skin protection, avoidance of allergens and irritants, and treatment with potent topical steroids. Alitretinoin can affect serum lipid profiles and liver function and appropriate monitoring is required.
Antipruritics act by counter-irritation, and are applied topically. Crotamiton relieves itching, partly by production of erythema and a feeling of warmth. Antihistamines block H1-receptors and reduce the swelling and irritation caused by the histamine that is released in response to injuries such as sunburn, insect bites and stings. Topical application may cause sensitisation and so antihistamines are best given orally, preferably as elixirs or syrups, to increase their rate of absorption. For systemic antihistamines see the Allergic Disorders chapter.