PRURITUS Treatment

Eczema, scabies, lichen planus and dermatitis herpetiformis are all associated with intense itch; and lichenification manifests itself chiefly as irritation. The treatment of these conditions is that which is needed to relieve the irritation ; but it sometimes happens that the irritation is overwhelming, dominating the patient and his household, and something more is required. On these occasions it is tempting to apply local anaesthetic and antihistamine preparations to the skin, but this is a temptation that should be resisted because these preparations are sensitizing agents. Sedatives are useful when given orally, and this applies also to antihistamines—which are valuable for their sedative and tranquillizing properties. A combination of promethazine hydrochloride 12-5 mg. and amylobarbitone 50 mg. is useful; but if promethazine causes undue drowsiness it can be replaced by triprolidine hydrochloride. In the elderly, however, barbiturates are often poorly tolerated ; they may produce a state of confusion and then the itch plays a disturbing and demoralizing role. In these circum­stances chloral hydrate is the best drug to use—after allowing a few days to, elapse without the use of any cerebral depressant drugs. For local treatment one should be content with simple applications of low sensitizing potential such as the lead compound lotion B.N.F., equal parts of linseed oil and lime water, or liquefied phenol 1 ml., zinc oxide 2 g., calamine 1 g, glycerin 2 ml., mag­nesium hydroxide mixture, B.P., to 30 ml. These preparations may be either painted on frequently or used as wet compresses. There is a place for corti­costeroids either as a spray (which is convenient for covering large areas quickly, but often making the skin feel uncomfortably dry), a lotion (if the surface is moist) or a cream or ointment if it is dry. It is justifiable in extreme cases to give a short course of oral corticosteroid treatment.

A separate problem arises when, in spite of the patient's complaint of intense irritation, nothing abnormal is visible except the marks that he has made by scratching himself. It is then necessary to identify the precipitating cause. There are many possible explanations : scabies, in a person who is so clean that few lesions develop ; pediculosis corporis which can be recognized by examining the seams of the underclothing ; senile change in the skin (for which testo­sterone or chlorpromazine are indicated) ; a side-effect of certain drugs such as morphine or carbromal (neither of which should be used by patients liable to pruritus or actually suffering from the condition) ; psychoses—when the patient usually presents the doctor with a folded piece of paper stated to contain "the insects" ; a manifestation of renal or hepatic disease with toxaemia ; a symptom heralding a metabolic disorder such as diabetes mellitus ; an accompaniment of blood dyscrasias including the leukaemias and polycythaemia vera ; and—fairly commonly—in lymphadenoma. This differential diagnosis, by no means exhaustive, may serve to emphasize the need for taking a detailed history and making a thorough physical examination.