Urticaria (Hives) is a condition in which there are raised red spots or eruptions of various size on the surface of the skin, often itchy, which come and go. It is usually an allergy to a drug or some food item. Urticaria may vary in size and may join together to form larger swellings.
What are the causes?
Urticaria is very common, especially in people who have experienced other allergic reactions. The eruptions usually occur in batches. Release of histamine and other chemicals into the bloodstream, associated with the allergic response, causes the itching, localized swelling, and other symptoms. Many substances, called allergens, can trigger the allergic response.
Common allergens include:
- Foods (such as berries, fish, nuts, eggs and milk)
- Animal dander (especially from cats)
- Insect bites
- Hives may also develop after infections or illness. There may be a hereditary tendency in the development of hives.
What are the symptoms?
Urticaria is characterised by sudden, acute skin eruption with swelling, redness, intense itching and burning. The urticaria eruptions may be irregularly shaped or round. They may be single or multiple.
- Red or skin coloured eruptions with clearly defined edges
- Sudden onset
- Rapid resolution
- Eruptions enlarge, spread, or join together to form large flat raised areas
- Eruptions change shape, disappear and reappear within minutes or hours
How is it diagnosed?
The diagnosis is primarily based on the appearance of the skin, and is confirmed by a history of exposure to an allergen. Occasionally, skin or blood tests may be performed.
In selected patients with urticaria, using the history and physical examination as guides, additional tests that may be considered include the following:
- Stool examination for faecal white blood cells, ova, and parasites
- Antinuclear antibody
- Hepatitis B and C screen
- Thyroid function tests
- Tests for complete blood count, prostate-specific antigen, and serum calcium, or other tests as directed
What is the treatment?
The best treatment for urticaria is to find and remove the cause. This is not an easy task and often not possible. Antihistamines are usually prescribed to provide relief. Antihistamines work best if taken on a regular schedule to prevent hives from forming. No one antihistamine works best for everyone, so the doctor may need to try more than one or different combinations to find what works best. In severe urticaria, an injection of epinephrine (adrenaline) or a cortisone medication may be needed.
Hives in the throat may obstruct the airway, so any swelling in the throat or difficulty in breathing are emergency symptoms. Immediate medical help is needed. Treatment may not be needed if urticaria is mild, and may disappear spontaneously.
Antihistamines, adrenaline, corticosteroids, sedatives, or tranquillisers may reduce the inflammation, itching, and swelling.
Cool compresses or soaks to the area may reduce swelling and pain. Avoid irritation of the area, and do not wear tight clothing which may trigger a new outbreak. Avoid known allergens to prevent recurrence of hives.
The condition may be uncomfortable, but it is generally harmless and the welts disappear on their own. In most cases, the exact cause of urticaria cannot be identified.
How can it be prevented?
- Avoid exposure to substances that are known allergen for you.
- Take only prescribed medications.
- Avoid hot baths or showers after an episode of urticaria to prevent recurrence.
- Avoid high protein foods at this time.