URTICARIA Treatment

Urticaria is the result of localized ædema in the skin produced by leakage of fluid without red cells from the blood. The transient increased permeability of the vessels is usually brought about through the release of histamine (or histamine-like substances), by a variety of stimuli including injury, and the occurrence of antigen-antibody reactions. Some skins weal abnormally with injury (dermo-graphism). Others weal through the action of heat, cold or light; and among the less common precipitating factors are emotional stress and hypnotic suggestion. Urticaria is a common disability, but it is often of limited duration and the eruption can usually be controlled with oral antihistamines. Further the search for the provocative stimulus is difficult and time-consuming, and not surprisingly the cause is seldom found. Some cases become chronic, and then it is imperative to identify the cause if rational treatment is to be given.

Provocative Stimuli.—The search for possible antigens should be directed to the diet, to drugs, to inhalants, to the contents of the hollow viscera and to the patient's own tissues.

The diet should be recorded day by day, with a note on the condition of the skin written on the adjacent page. Things that have been eaten in the 24 hours preceding each fresh outbreak should be reviewed and any foodstuff common to each incident noted. All suspicious foods should be banned. If the urticaria disappears, the foods can be added one by one at intervals of a week and the results observed. If the true cause has been found it should be possible to make the urticaria appear and disappear at will by introducing and withholding it from the diet. Failing this the patient can be starved for two days, except for water ; persistence of the urticaria would make a dietary cause most unlikely. If the diet is suspected but observation has failed to identify the cause, skin tests may be successful provided that the test solutions used are potent.

Of drugs, penicillin and aspirin are said to be the commonest causes of chronic urticaria. The eruption can outlast the giving of penicillin by many months—possibly due in part to the ingestion of traces of penicillin in milk and partly by inhalation, for example in hospitals. Aspirin often acts as a non­specific stimulus by aggravating urticaria due to other causes. A diary is necessary as in the case of the diet. One should remember that drugs can be taken unwittingly—for example quinine in drink and phenolphthalein in tooth­paste ; and also that drugs can be ingested, injected, inhaled, anointed or placed in any of the natural orifices.

Inhalants, such as mould spores, dusts and pollens, which do not necessarily cause sneezing or ocular discomfort, produce a seasonal or intermittent pattern of attack according to the climatic conditions under which they are produced, or their location. Skin testing facilitates precise identification, but specific desensitization may not be practicable.

The hollow viscera, such as the gut and gall bladder can contain organisms or products of their activity which are absorbed and act as antigens. Yeast infection of the bowel or of diverticulae of the bowel (including blind loops left by surgery) often causes urticaria.

The patient's tissues may harbour infections such as dental infection or a tumour which is breaking down rapidly, and these can act as antigens. The auto-antibody disease, lupus erythematosus in its disseminate form, can present as urticaria, and so can the vascular disease, polyarteritis nodosa

Emotional stimuli can be entertained as factors only when, in addition to a lack of physical causes, there are positive psychological ones. Suppressed anger at some intolerable but apparently irremediable situation is a potent stimulus.

Symptomatic Treatment.—In many cases none of the above causes can be found and then the only available treatment is symptomatic. The antihistamine drugs, taken by mouth, are usually effective but it may be necessary to find by trial and error which drug suits the individual patient. The intramuscular injection of an antihistamine is worthy of trial if the response to oral treatment is poor. One of the chief anxieties about antihistamine treatment in the ambulant patient is its possible effect on the ability to handle machinery, particularly motor cars and aeroplanes, for even if antihistamines do not have an hypnotic effect they may impair judgment. The object is first to suppress the eruption with, for example, between 0-15 g. and 0.3 g. of diphenhydramine hydrochloride in divided doses daily, and then to find the minimal dose that will just control the eruption. Children tolerate these drugs well and for them elixirs are very acceptable. An alternative to the antihistamine drugs is to use chloroquine by mouth, for example from 0.25 g. to 0.5 g. of the phosphate daily; but chloro- quine given for long periods has important side- and toxic effects. Corti­costeroids usually control urticaria but their use is justifiable only to tide the patient over an acute attack, particularly when the precipitating stimulus is known and can subsequently be avoided—as in urticaria caused by penicillin, In fulminating attacks or when the airway is threatened by ædema, adrenaline hvdrochloride solution, i ml. (i in 1000), is given subcutaneously. These circumstances also warrant giving hydrocortisone hemisuccinate parenterally.