Urticaria is characterised by weals (hives) or angioedema (swellings, in 10%) or both (in 40%). There are several types of urticaria. A weal (or wheal) is a superficial skin-coloured or pale skin swelling, usually surrounded by erythema (redness) that lasts anything from a few minutes to 24 hours. Usually very itchy, it may have a burning sensation. Angioedema is deeper swelling within the skin or mucous membranes, and can be skin-coloured or red. It resolves within 72 hours. Angioedema may be itchy or painful but is often asymptomatic. Papular urticaria (Insect bites) are localised, often clustered in groups of 3–5 lesions, and they appear in crops. Bites persist for days. Urticaria is classified according to its duration: Acute urticaria (< 6 weeks duration, and often gone within hours to days). Chronic urticaria (> 6 weeks duration, with daily or episodic weals).
Chronic urticaria may be spontaneous or inducible. Both types may co-exist. Inducible or physical urticaria includes: symptomatic dermographism, cold urticarial, cholinergic urticarial, contact urticarial, delayed pressure urticarial, solar urticarial, heat urticarial, vibratory urticarial, and aquagenic urticarial. Chronic spontaneous urticaria affects 0.5–2% of the population. Weals are due to release of chemical mediators from tissue mast cells and circulating basophils. Acute urticaria can be induced by the following factors but the cause is not always identified. acute viral infection, acute bacterial infection, food allergy ,drug allergy Drug pseudoallergy—aspirin, nonselective nonsteroidal anti-inflammatory drugs, opiates; Food pseudoallergy—salicylates, azo dye food colouring agents such as tartrazine (102), benzoate preservatives (210-220) and other food additives these cause urticaria without immune activation.
There are no routine diagnostic tests in chronic spontaneous urticarial. But investigations may be undertaken if an underlying disorder is suspected. The main treatment of all forms of urticaria in adults and in children is with an oral second-generation antihistamine. For chronic urticaria this has to be continued for prolonged periods. Conventional first-generation antihistamines such as promethazine or chlorpheniramine are no longer recommended for urticaria due to side effects. If non-sedating antihistamines are not effective, a 4 to 5-day course of oral prednisone (prednisolone) may be warranted in severe acute urticaria. It should not be taken for long periods. There is good evidence to support treatment omalizumab or ciclosporin in antihistamine-resistant patients.