Dr David L. J. Freed, MB, MD, MIBiol
Once the bane of the dermatology departments, this unpleasant and sometimes dangerous affliction is another of the "new allergic conditions", and very rewarding to treat. About 50% respond to simple dietary avoidances. The common triggers in this case are the artificial food additives, in particular azo dyes (E102, E104 etc) and preservatives (6). Fruits can also be a major problem. Remember to warn all patients and their relatives that a sweet drink that proudly claims to contain "no artificial flavourings or colourings" will probably still contain preservatives - close perusal of the small print on the label is mandatory.
Cases that fail to respond to the simple diet will require more complex diets and desensitization, and I have sometimes encountered unexpected allergies. I recall one woman who turned out to be allergic to her husband's semen; fortunately it proved easy to desensitize. Chronic urticaria is one condition in which I have to concede partial defeat fairly often, in that they improve but do not lose the problem completely. I assume this is because of exotic sensitivities that I have not tracked down, and the cost-effectiveness of further detective work is dubious. In this case I will prescribe the little-known antiprotease drug tranexamic acid (Cyclokapron), which has an unexplained beneficial effect far greater than that of antihistamines or steroids (7). The patient should take one 0.5 G tablet at the first sign of an attack, then a further tablet every half-hour, up to a maximum of 30 tablets per day or until the attack starts to subside. Side-effects include nausea and hypotension and there is a theoretical risk (not so far seen in practice) of enhancing any thrombotic process.
Angioedema affecting the larynx is potentially life-threatening and you dare not play around with it. Issue the patient with a self-injection kit of adrenaline and make sure he/she knows how to use it accurately and swiftly, even in half-light or when half-swooned. The kit must be carried on the person, not in the handbag or in the car. The side-effects of adrenaline are trivial in comparison with the risk of sudden death and the patient must be told emphatically that they are to self-inject immediately there is the slightest hint of an attack. They must NOT fool around with clothing or alcohol swabs; the needle must be thrust straight through the clothing into the nearest limb, subcutaneously, and the patient must report to Casualty immediately afterwards. It is far preferable to be embarrassed once or twice by false alarms, or even to have an abscess from a dirty injection (most unlikely), than to suffocate to death.
References
6) Supramaniam G, Warner JO: Artificial food additive intolerance in patients with angio-oedema and urticaria. Lancet 1986, ii: 907-9.
7) Freed DLJ, Buisseret P, Lloyd M et al: Angioedema responding to antiprotease therapy but without abnormality of the complement system. Clin Allergy 1980, 10: 21-23.
