Hives (Urticaria)

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What is Hives?

Hives, or the medical term 'Urticaria' is a common allergic reaction on the skin. It is characterized by raised, red skin welts that are more than 5mm in diameter. Hives are extremely itchy, and often have a pale border surrounding the red area. The urticarial rash can be isolated or many, sometimes they join together and form a large area of raised, red rash.

Who gets Hives?

Urticaria is a common disease - it affects up to 25% of the general population.

Predisposing Factors

There is no specific predisposing factors for urticaria. Geographical regions do not have any influence on cases of urticaria. The number of cases are similar internationally.

Acute urticaria happens equally in men and women; but chronic urticaria seemed to be more common in women.

Urticaria happens in all ages, but chronic urticaria is more common in the 40-50s.

Progression

Urticaria is divided into 2 forms according to the duration of disease:

acute: lasting <6 weeks

chronic: lasting >6 weeks

Acute urticaria is more common than chronic one. More than two-thirds of the cases of urticaria are acute. The rashes of acute urticaria are characterised by a rapid onset and rapid resolution within several hours. A trigger can occasionally be identified.

As for chronic urticaria, it account for approximately 30% of the cases. Clinically both acute and chronic forms are indistinguishable. However resolution time in chronic urticaria is longer - sometimes up to 36 hours before resolution.

The following are the recognised causes or associations of urticaria:

autoimmune diseases: thyroid diseases

drugs: antibiotics (penicillins, etc), sulfur containing medications, progesterone (oral contraceptive pills, hormone replacement therapy), local anaesthetic agents, opiates, etc.- physical contact: animal saliva, plant products, resins, raw fish, vegetables, latex, metals (nickel)

stinging insects: bees, wasps, hornets

aeroallergens: allergens that travels in the air, like pollens, grass, weeds.

foods: milk, egg, peanuts, nuts, soy, wheat

infections: acute bacterial and viral infections such as Coxsackie A/B, hepatitis A/B/C, parasitic infections

physical agents: pressure, cold, heat (in exercise, sweating, hot showers causing cholinergic urticaria)

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