Hives are relatively common with at least 20% of the population having had at least one episode during their lifetime. Although seen in all ages, they seem to be more prevalent among young adults.
The causes of urticaria are many and in 80% of cases never determined; not knowing the cause often results in an on-going problem. The most common causes of chronic urticaria are drug reactions, stress, food sensitivities and fungal infections. Some initiating factors include:
Lab findings are often unremarkable in cases of acute urticaria. For chronic urticaria, lab work should include CBC, ESR, UA, histamine levels and dental/sinus examinations to rule out hidden pathology.
Instead of just treating the symptoms (which is obviously important as well), a physician needs to get to the bottom (if there is one) of why the patient is getting them in the first place.
Acute urticaria lasts from 1 to 7 days and treatment is not usually needed except to reduce the itching. The inciting agent must be dealt with, be it food, external agent or an emotion. In severe cases, epinephrine, as found in a bee sting kit, may be required.
In cases of chronic urticaria of over three weeks' duration, 50% of patients experience spontaneous remission within two years, even though in the majority of cases the cause is never identified.
In extreme cases, swelling in the throat may lead to a medical emergency.
Foods and drugs are common causes of hives. A reaction that occurs immediately after ingestion of certain foods, producing hives and difficulty breathing is termed anaphalactic and is potentially dangerous. Delayed reactions are less serious but more difficult to pinpoint. Some patients get hives occasionally only when they ingest a specific food or food additive. Others develop hives as a chronic problem that can continue for years. Most studies of chronic hives suggest that only a low percentage are due to food allergy; this is usually because diet revision attempts were inadequate for revealing the hidden food causes.
Amongst patients with chronic hives and either treated hypothyroidism or a normally functioning thyroid gland, it is reasonable to test for anti-thyroid antibodies. In a study of 10 patients with chronic hives, thyroxine (T4) was administered for a minimum of 12 weeks. Of 7 patients with elevated anti-thyroid antibodies at baseline, all had complete resolution of hives or marked improvement within 4 weeks. Two patients required an increase in the thyroxine before complete resolution was seen. In 2 others, already on thyroxine therapy for hypothyroidism, an increase in the dose also resulted in resolution of the hives.
The initial dose was on average 100mcg per day, which was increased if the initial dose failed to produce clinical improvement. The highest dose used was 250mcg per day. The 3 patients without elevated anti-thyroid antibodies did not respond to thyroxine therapy. There was a recurrence of hives after treatment was stopped which resolved again after treatment was restarted. There was no consistent correlation between improvement in symptoms and reduction in thyroid antibody levels. [J Allergy Clin Immunol 1995;96: pp.901-5]
Some forms of chronic hives have an autoimmune origin which means, in about 30% of patients, that the immune system is producing antibodies against normal substances in the body and triggering the release of histamine by mast cells. [Journal of the American Academy of Dermatology, March 1999, 40(3); pp.443-450]
For many patients with hives of unknown cause, treatment with antihistamines is effective. This is because in people with hives, histamine is being released by mast cells in the tissues which in turn initiates the irritation and accumulations of fluid. Other inflammatory white blood cells, including lymphocytes and polymorphonuclear cells, have also been implicated. Antihistamines inhibit this inflammatory process.
On occasion and especially with pressure hives, antihistamines are ineffective, probably because of the nature of the molecular mediators operating in this condition. If antihistamines do not help, then several second-line treatments are used. The most effective are corticosteroids. Others include doxepin, dapsone, attenuated androgens, calcium antagonists, antimalarials, gold and methotrexate.
A study suggests that administration of thyroxine to patients with chronic urticaria associated with elevated thyroid antibodies can result in remission of the hives. [J Allergy Clin Immunol 1995;96: pp.901-5]
An alkaline sponge bath may be helpful to reduce the itching. Add one teaspoon of baking soda to each pint of very hot bath water and soak.
Food additives that have been shown to trigger hives include colorants (azo dyes), flavorings (salicylates), artificial sweeteners (aspartame), preservatives (benzoates, nitrites, sorbic acid), antioxidants (hydroxytoluene, sulfite, gallate), and emulsifiers/stabilizers (polysorbates, vegetable gums).
Lack of hydrochloric acid (HCl) secretion by the stomach has been linked to chronic hives probably as a result of increasing the likelihood of developing food allergies. In one study of 77 patients with chronic hives, 24 (31%) were diagnosed as having achlorhydria, and 41 (53%) were shown to be hypochlorhydric. [Rev Gastroenterol 1951;18: pp.267-71]
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