What are hives?
Urticaria (sometimes called hives) is raised, red, itchy areas on the skin that appear as an allergic skin reaction. Urticaria is classed as:
- Acute urticaria – if it develops suddenly and lasts less than six weeks. About 1 in 6 people will have at least one bout of urticaria in their life. It can affect anyone at any age. Some people have recurring bouts of acute urticaria.
- Chronic urticaria – if it persists longer than six weeks.
How do they occur?
Often no cause for hives can be identified. Clusters of hives may appear as an allergic reaction to an irritant such as food, medicine, an insect bite or sting, infection, or emotional stress. Histamine, a chemical your body makes, is released in response to the irritant that causes the hives to form.
What does the rash of acute urticaria look like?
The rash usually appears suddenly and can affect any area of skin. Small raised areas called wheals develop on the skin. The wheals look like mild blisters and they are itchy. Each weal is white or red and is usually surrounded by a small red area of skin, which is called a flare. Sometimes wheals next to each other join together to form larger ones. Each weal usually lasts less than 24 hours. However, as some fade away, others may appear. It can then seem as if the rash is moving around the body.
Are there any other symptoms associated with hives?
- In some cases a condition called angioedema develops at the same time as urticaria. In this condition some fluid also leaks into deeper tissues under the skin that causes the tissues to swell. The swelling of angioedema can occur anywhere in the body but most commonly affects the eyelids, lips and genitals.
- A variation called vasculitic urticaria occurs in a small number of cases. In this condition the wheals last more than 24 hours, they are often painful, may become dark red, and may leave a red-pigmented mark on the skin when the weal goes.
How is it diagnosed?
Your health care provider will look at the hives and ask about your history of sensitivity to such things as:
- Animal fur
- Exposure to heat, cold, or sunshine.
- Viral infection such as a cold or flu can trigger an urticaria rash in some people.
- 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 localized rash appears when the skin is physically stimulated. The most common is called dermographism when a rash develops over areas of skin that are firmly stroked.
How is it treated?
He or she may suggest that you do one or more of the following to relieve the itching and reduce the swelling:
- Use cool compresses.
- Avoid heat or rubbing.
- Menthol 1% in aqueous cream can help with itching, although if it is left on for too long the itch may come back.
- Take antihistamine medicine to reduce your allergic response.
- If you can identify a trigger such as a food, then it would be sensible to avoid it in the future.
- A short course of steroid tablets is sometimes prescribed in severe cases to help reduce swelling in the skin.
- If extra control is needed you may be prescribed an anti-leukotrines medicine.
How long will the effects of hives last?
The effects of hives can last from a few hours to several weeks or months. In most cases the hives eventually go away without treatment, but taking drugs such as antihistamines help the hives go away faster. Chronic hives last a longer time. Most often (more than 50% of the time) it is not possible to determine their cause. Antihistamines are usually very helpful.
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