Urticaria is an allergic skin rash also known as ‘nettle rash’ or hives. There are two distinct types: acute urticaria is often caused by an allergy and can last between several hours and six weeks; chronic urticaria persists beyond six weeks. Most hives go away within days to a few weeks. Occasional unlucky individuals will have itches and swellings that come and go over many years. Urticaria is classified as either acute or chronic. Acute urticaria is defined as urticaria that has been present for less than 6 weeks. Chronic urticaria is defined as urticaria that has been continuously or intermittently present for at least 6 weeks. The 6-week period is a guide and not an absolute demarcation.Skin lesions and pruritus occur, caused by an allergic or nonallergic mechanism.
Urticaria occurs following release of histamine, bradykinin, kallikrein, and other vasoactive substances from mast cells and basophils, resulting in intradermal edema from capillary and venous vasodilation and occasionally from leukocyte infiltration. Urticaria has four major mechanisms. Most commonly, it is a manifestation of acute immunoglobulin E (IgE)mediated hypersensitivity with histamine and other vasoactive peptides released from mast calls and basophils. Nonimmunologic urticaria occurs when an exogenous substance results in mast cell degranulation either by direct stimulation of the mast cell or by unknown mechanisms (reaction to intravenous contrast dye). Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) cause urticaria by a nonmast cell mechanism, especially in asthmatics.
Causes of Urticaria
4.Urticaria and alcohol.
5.Emotional factors( emotionalstresses).
Symptoms of Urticaria
Treatment of Urticaria
Oral antihistamines control wealing and itching for the majority of patients with urticaria. Avoid aspirin and codeine. It is usually safe to take paracetamol and the newer Cox-II inhibitor anti-inflammatories and avoid alcohol. Non-sedating antihistamines (loratidine, fexofenadine, terfenadine, cetirazine, and astemizole) are less likely to cause drowsiness than the less expensive conventional antihistamines. They may be unsuitable in pregnancy. Terfenadine and astemizole may increase the risk of abnormal heart rhythms. They should be avoided if you have heart disease or you are also taking erythromycin, ketoconazole and some other medications. Fexofenadine, loratidine, desloratidine and cetirazine are safe. Oral steroids (prednisone) are useful for severe acute urticaria but unsuitable long term because of serious adverse effects. Antifungal agents, used to clear an assumed underlying infection.