What causes acute urticaria (hives)?
A 'trigger' causes cells in the skin to release chemicals such as histamine. The chemicals cause fluid to leak from tiny blood vessels under the skin surface. The fluid pools to form weals. The chemicals also cause the blood vessels to open wide (dilate) which causes the flare around the weals. The trigger is not identified in about half of cases. Some known triggers include:
- Allergies - for example:
- Food allergies such as allergies to nuts, strawberries, citrus fruit, egg, food additives, spices, chocolate, or shellfish. Sometimes you can develop an allergy to a food even if you have eaten it without any problem many times before.
- Allergies to insect bites and stings.
- Allergies to medicines such as penicillin, aspirin, anti-inflammatory painkillers, etc.
- A viral infection such as a cold or 'flu can trigger an urticarial rash in some people. (You 'react' to the virus.) A mild viral infection which causes few other symptoms is probably a common trigger of an urticarial rash that develops without an apparent cause.
- Skin contact with 'sensitizers' causes a local area of urticaria in some people. For example, chemicals, latex, cosmetics, plants, ointments, nettle stings, etc.
- Physical urticaria. This is when a localised rash appears when the the skin is physically stimulated. The most common is called dermographism when a rash develops over areas of skin which are firmly stroked. Sometimes an urticarial rash is caused by heat, cold, emotion, exercise, or strong sunlight.
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Where to next?
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yvonne thomas, over 2 years
hi, i have had urticaria now for six /seven weeks it started as an itch on my back with spots which was very uncomfortable then it started to spread and i ended up with most of my back looking and feeling like i had severly burn it .after the third week i had to go on the sick because of the pain ,i also had this rash on my hip only on one side and it ended up spreading down to the top of my leg which also looked and felt like i had been burnt.i have been prescribed antihistamine in various strengths and i am still on 180mg plus steroid creams of different strengths i am now on the strong steroid cream . i had to take antibiotics after a few weeks as i had a slight infection at the top of my back ,but this cleared up after a week. after all this time it has started to clear up but very slowly and my back and side is still itchy and very painful if iscratch it feels like the nerve endings have been damaged and i am finding it difficult to wear any clothes . i have tryed a soft bra which is a size larger than normal , but my skin is still very sensitive and i have to wear jogging bottoms at present which are a size larger than normal to relive any pressure. i did have it in other places on my body ,but because i had the steroid cream at hand i could clear this up very quickly.any help with clearing this up as i need to get back to work a.s.a.p.
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