Why Do Hives Itch?

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What are hives?

Hives is a common skin condition which results in itchy, blotchy reddish patches which can occur on any part of the body. They are intensely itchy at their onset. Medically this condition is known as Urticaria, which is a transient swelling of the skin with loss of fluid from surrounding tissues. The skin lesions appear suddenly and go away as fast as they appeared; the skin appears completely normal afterwards. It is basically an allergic reaction to a food, drug or any other physical stress. Hives is a common cause for skin inflammation. Individual lesions last for less than 12-24 hours. Cases which are chronic last for more than 6 weeks. Up to 20% of population suffer from this skin condition. This condition can recur and there is no permanent cure.

The exact cause for this rash still remains elusive. There are many trigger factors which result in different types of urticarial rashes which clear within 24 hours. Foods like nuts and shell fish are very often implicated to stimulate this rash. There can be other substances like medications like salicylates or food dye substances. Whatever maybe the allergen, it results in wheal formation which are elevated and itchy patches.


Itching of hives occurs due to a chemical called histamine released by the cells in the skin. The exact mechanism postulated is that certain foods or any trigger factor causes certain cells in the skin known as mast cells to release a chemical substance called histamine. Due to histamine released by mast cell granules, it results in increased skin permeability resulting in escape of fluid into surrounding tissues. This results in severe swelling of the skin and causes severe itching. The reduction in itching with antihistamine compounds proves histamine as the main mediator. Immune system of an individual plays an important role in the activation of various pathways within the body which cause release of chemicals called antihistamines.

Many medications and drugs cause direct release of histamine by direct degranulation or irritation of mast cells without involvement of the immune system. Many foods like strawberries, milk, shellfish and nuts also cause direct release of histamine. Thus histamine is the chemical responsible for the hives, redness and swelling of the skin lesions. There is also dilatation of surrounding blood vessels which causes increased blood flow.

Rashes can also be caused by cold, heat, bee sting, wasp sting, pressure and trauma. Many a times, excessive scratching can also aggravate and lead to wheal formation.


As far as possible, the cause of urticaria should be found out and eliminated. To decide whether a food is responsible, elimination and trial diets are advocated even though they are cumbersome .Medications and drugs suspected should be avoided.

Antihistamines are the most effective drugs for treatment of urticaria and the itchiness associated with it. Antihistamines are given to block the effect of the chemical histamine, the major chemical responsible for the itch and rash. In a restless patient, a sedative antihistamine maybe prescribed.

Complaints of generalised itching with, on occasions nothing to see may prompt doctor to label patient as psychotic.


Hives is a common skin rash that results in reddened elevated circular patches due to an allergic reaction. Itching is due to a chemical released by the cells in the skin known as histamine. There are a number of trigger factors which cause the rash to appear. The chemical histamine is responsible for the itch and redness of the skin. Treatment is mainly in the form of antihistamines .This condition can reoccur from time to time.

Author: rachita

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