Drugs used to control itching, a condition also known as pruritus
Antipruritic drugs are used to relieve itching, a symptom with a variety of possible causes, including inflammation or dryness of the skin, allergy, hormone deficiency in older women, exposure to irritant substances, and skin infections and infestations. Scratching the skin may cause further inflammation and itching, which may continue after the initial cause of the itching has disappeared.
This cycle may be broken by the use of antipruritics, which can be applied to the skin or taken orally. Most antipruritic drugs are available over the counter. However, itching should be investigated by your doctor in case there is an underlying cause that needs specific treatment. If you have an infection or infestation, you may be prescribed an alternative treatment (see Preparations for skin infections and infestations).
The main types of antipruritic drug include topical corticosteroids, antihistamines, local anaesthetics, and soothing preparations, such as emollients (see Emollients and barrier preparations). A topical corticosteroid can help to relieve itching caused by skin inflammation; antihistamines may be used to relieve itching caused by an allergic reaction; local anaesthetics numb small areas of skin, reducing itchiness caused by insect bites or stings; and soothing preparations ease itching caused by a variety of disorders, including eczema.
A corticosteroid preparation may be applied to the skin to reduce inflammation and thereby relieve itching caused by skin conditions such as psoriasis, contact dermatitis, or eczema. Corticosteroids affect a wide range of body processes, including virtually all aspects of the inflammatory process. Their exact mechanism of action is unknown, but one of their effects is to reduce the production of substances called prostaglandins, which play a key role in triggering inflammation.
Topical ointments or creams that contain antihistamine are commonly used for localized itching, such as that caused by an insect bite or sting. Widespread itching that is caused by a disorder such as chickenpox can often be treated more effectively with an oral antihistamine.
Antihistamines relieve itching by inhibiting the action of histamine, which is produced by body tissues in response to tissue damage or the presence of an allergen (a substance that triggers an allergic reaction, such as wasp venom). Histamine causes itching, swelling, and other symptoms of allergic reaction.
Topical antihistamines may themselves cause an allergic skin reaction, and you should stop using the product if additional irritation occurs. Certain oral antihistamines may make you feel drowsy, which can be useful if itching has prevented you from sleeping.
Small regions of skin irritation, such as those caused by insect stings or bites, may be soothed using a local anaesthetic cream or spray. These products stop itching by blocking the transmission of impulses along the nerves in the affected area. Local anaesthetics are inappropriate for widespread itching and can worsen symptoms by causing an allergic reaction in the skin.
Itching, such as that caused by insect bites, sunburn, or an allergic rash such as urticaria, can often be soothed using calamine lotion or cream or an emollient. Emollient preparations reduce moisture loss from the skin, preventing dryness and easing itching, and can be used to relieve the symptoms of eczema, psoriasis, and other dry skin conditions.
Do not apply an antipruritic drug to broken or infected skin except on the advice of a doctor.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.