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Urticaria (Hives) and Angioedema

Urticaria (commonly known as hives) are mosquito bite like swellings on the surface of the skin that range in size from a few millimetres to several centimetres. They may last minutes or hours and can change shape from round to oval, forming rings or patches. The skin swelling seen in urticaria is due to the release of chemicals such as histamine from mast cells in the skin that causes small blood vessels to leak. They are often itchy, but sometimes may not be itchy at all.

Common causes of hives are infection or contact with plants/animals as well as allergic reactions to food and medication.

Urticaria (Hives) and Angioedema Help Sheet

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Urticaria (common names: hives, weals, wheals, nettle rash) is an intensely itchy rash that may occur in children and adults. It may occur alone or be part of a more generalised allergic reaction. It is frequently the first symptom in such a reaction to a food or medication.

The skin swelling seen in urticaria is due to the release of chemicals such as histamine from mast cells in the skin that causes small blood vessels to leak. The hives can be a few millimetres or several centimetres in diameter, coloured white or red, often surrounded by a red flare. They may last minutes or hours and can change shape from round to oval, forming rings or patches .

Hives are very superficial swellings on the skin and may be accompanied by deeper swellings, particularly around the eyes, mouth, hands, feet and elsewhere. These deeper swellings are referred to as angioedema and rather than itch, they may be painful or tight. They usually occur with hives but can occur alone.

There are many forms of urticaria and it may occur for no apparent reason or may be associated with a trigger.

There are acute and chronic forms of urticarial / angioedema.

urticariaAcute Urticaria – this may be a one off episode or an episode may last a few days or 2-3 weeks. It is often caused by an allergy with the most common causes being medication, food or a sting.

Many forms of urticaria are not due to an allergy but the rash may be associated with infection, especially in children.

Chronic urticaria is a term we use when hives appear a few times a week for more than six weeks. This form is rarely caused by an allergy and often has an underlying immune cause.

Physical urticaria is one subgroup of chronic urticaria. In these forms, the characteristic rash appears as a result of exposing the skin to heat, cold, vibration or sunlight , to name a few of the recognised physical triggers.

The first line of treatment for any urticaria is the use of antihistamines which can be very helpful in controlling itch. Sometimes higher than usual doses are recommended but this must be prescribed by your doctor.

There are a number of general measures that people who experience urticarial/ angioedema may find helpful.

  • Keep cool and wear looseclothing.

  • Avoid alcohol as this may make an attack of hivesworse.

  • Stress can also be responsible for worsening urticaria.

Most people with chronic hives are warned to avoid certain medications such as aspirin or non steroidal anti inflammatory drugs as these may cause a severe flare – if you have a reason for taking these medications, discuss this with your doctor for specific advice. Paracetamol is generally well tolerated.

urticaria handAs there are many causes of urticaria a consultation with your doctor is important to exclude certain causes and to explore whether further investigations or referral is necessary. If angioedema occurs without any hives at all your doctor will want to perform some specific blood tests to eliminate some very rare causes of this. Most often however, angioedema is caused by the same things that trigger urticaria.

For more information go to www.allergy.org.au/patients/skin-allergy/urticaria-hives

Prepared by Professor CH Katelaris November 2012

Content updated November 2012

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