This article was first published in I CAN! newsletter December 2007 issue. Used with permission.
Urticaria, commonly termed as "hives", is an itchy rash that may appear anywhere on the body as localised swellings of the skin that last from anywhere between 2 to 48 hours before fading away. It results from release of chemical substances (mainly histamine) by specific cells, triggered by either an allergic or non-allergic reaction. This condition affects an estimated 20-30% of the population, at one time or another in their lives.
When urticaria develops in loose connective tissues such as the eyes or lips, the affected area may swell excessively and the reaction is called "angioedema". Angioedema may be itchy but may also be painful, numbing or burning. The time course of angioedema is similar to that of urticaria.
Acute urticaria is defined as urticaria which disappears within 6 weeks. It is fairly common in children. The most common cause is infection (viral or bacterial induced), i.e. common cold, strep throat, infectious mononucleosis and hepatitis. Other less common causes include drugs (pain killers, antibiotics like penicillin, sulphonamides), specific foods (such as eggs, peanuts, shellfish, milk, etc.), food preservatives, reactions to insect bites, contact with chemicals/allergens or sometimes in 20%, no identifiable trigger can be detected. The need for further evaluation and treatment would depend largely on the severity of symptoms.
Chronic urticaria on the other hand occurs almost daily and lasts for more than 6 weeks. It can occur in children or adults. In the majority of cases, the cause of chronic hives cannot be identified despite detailed history and testing. In this instance the condition is called idiopathic urticaria and it is mostly a benign condition that resolves over time (usually in 6 months). The condition is not serious and symptomatic therapy (usually with anti-histamines) is all that is necessary. Very often, patients with chronic urticaria request for allergy testing. However, these tests are usually negative and not helpful. The best way to decide if allergy testing is necessary is for the patient to be seen by an allergy doctor. Based on detailed questioning and examination, the doctor will decide if further tests are necessary.
Another possible cause of chronic urticaria is physical urticaria which is usually obvious from the history of rashes appearing at areas exposed to extremes in temperature or pressure. Another type of physical urticaria is dermatographism, in which hives appear within a few minutes of scratching along an area of skin following the path taken by the act of scratching.
Rarely, your doctor may decide to perform more tests as there are some very uncommon causes of chronic urticaria. These include autoimmune diseases (systemic lupus erythematosus, autoimmune thyroid disease) and internal diseases (hyperthyroidism). If these secondary causes have been excluded and the rash is troublesome, a 3 to 5 day course of steroid treatment could be considered. But in most cases of chronic urticaria, the hives will gradually disappear over time.
Treatment for urticaria largely depends on the severity of symptoms presented. Mild hives are self-limited and usually require no treatment or, at the most, a mild anti-histamine for symptomatic relief. Sometimes, antihistamines may need to be taken on a regular basis to prevent the formation of hives. To avoid side-effects like drowsiness, non-sedative antihistamines (loratadine, fexofenadine) are available.
Antihistamine creams are ineffective. Supportive measures include cooling the affected area with a fan, cold flannel, ice pack or soothing moisturising lotion aids. If a trigger is identified, it should be avoided.
If the urticaria is generalised and severe as with angioedema, treatment should be similar to that for an anaphylactic reaction (i.e. shock). In addition to antihistamines, the mainstay of therapy in this case is subcutaneous epinephrine. Steroid treatment is rarely necessary. Some patients suffering from recurrent urticaria with known cause (i.e. food, insect stings) should be encouraged to carry and trained to use injectable epinephrine. Corticosteroids should be prescribed only as a last resort in children with acute and chronic urticaria. If symptoms persist despite the above treatment, a consultation with an allergist would be useful.
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