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Urticaria is the commonest allergic dermatosis because almost every individual suffers from urticaria at one time or the other during one's lifetime. Most people are familiar with the manifestations and consider it to be synonymous with allergy, not realising that urticaria is just one of the manifestations of allergy.
Urticaria manifests as sudden eruptions of itchy swellings (wheals) which may appear on any part of the body. The wheals may be of any size, the smallest being 2 to 3 mm, while the large ones may be 10 to 15 cm or even larger. The larger wheals tend to develop various shapes and are usually irregular. The most characteristic feature of urticaria is that the wheals disappear even without any treatment within a few minutes or hours. No lesion persists for longer than 24 hours.
Urticaria is generally not associated with any manifestations in the body. Severe attacks however, may be associated with pain in the abdomen, headache or nausea and vomiting. Generalised attacks may lead to a fall in blood pressure. One type of urticaria, which is based on the mechanisms involved is serum sickness, may be associated with joint pains, fever, involvement of the kidney and rarely other manifestations. In children however, severe attacks are often associated with high fever without any other manifestations or abnormality.
Causes
Urticaria can be caused by a variety of agents, each of which produces 'a characteristic pattern and frequency of the attacks. An accurate record of the pattern of recurrences is important to suspect the causal agent.
Emotional Urticaria
Some people experience attacks of urticaria whenever they are emotionally upset. The attacks stop recurring when the cause of emotional tension disapears but recur when the patient is tense again. These patients are distinct from cholinergic urticaria because they do not react to the heat stimuli or exercise. For treatment, such patients need psychiatric consultation and anti-allergic drugs, whenever necessary.
Urticaria Due to Insect Bites
Bites from bees, wasps and less commonly other insects often lead to pain and swelling because the stings of these insects often contain substances which mimic allergic reactions. Such a reaction occurs in almost every normal individual. His usually localised and disappears within a few hours. Some individuals however, who happen to have developed allergic hypersensitivity to the sting, can develop a generalised urticarial reaction which may also lead to a fall in blood pressure (anaphylactic reaction) and death. The generalised reaction is more likely to occur in individuals who work with these insects (bees).
Some persons' develop allergic hypersensitivity even to mosquitoes and less commonly to other household insects and develop urticaria whenever bitten by mosquitoes / other insects.
Very rarely, urtitarial reaction, have been noticed following contact with water or other materials of vegetable/ animal origin.
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