The Australasian Society of Clinical Immunology and Allergy

Hives (also known as urticaria or angioedema) look like mosquito bites. Although some unlucky individuals can have them every day for weeks, individual lumps usually disappear within minutes to hours. In most, hives are not due to allergy.

Version 2 February 2001.

What are hives?

Hives (also known as urticaria) look like mosquito bites. They range from the size of a pinhead to that of a dinner plate. Although some unlucky individuals can have them every day for weeks, individual lumps usually go in minutes to hours. In most people, hives are not due to allergy.

Hives are common

Approximately 1 in 6 people will develop hives some time during their life and are most common in children. They eventually disappear in most people. They may reappear following infection, when under stress or for no particular reason.

Hives occur in the skin

Underneath the lining of the skin, gut, lungs, nose and eyes are mast cells. These are designed to kill worms and parasites. Mast cells are like "land-mines", and contain "bags" filled with irritant chemicals including histamine. When these are released in small amounts, they cause local itch and irritation. In larger amounts, they will cause fluid to leak out of blood vessels, resulting in swelling of the skin. Occasionally, hives may not be itchy at all.

Can hives occur anywhere else?

Swelling of the lips and face is uncomfortable and cosmetically embarrassing, but is not dangerous. Around 1 in 3 people with hives will also have swelling of the tongue and throat. This is called angioedema. Occasionally the swellings will occur inside the stomach and cause tummy pain or cramps.

Sometimes the swellings can be dangerous

Hives on the outside don't harm us. They are not damaging inside organs like kidneys, liver or lungs. The only danger is if the tongue swells or the back of the throat swells severely. Since this can cause difficulty breathing, it is a symptom that needs to be taken seriously. Urgent medical treatment is required if this occurs.

Hives are rarely caused by terrible disease

Hives are rarely due to a nasty underlying disease. Common causes include infection (particularly in young children), or contact with animals or plants. Allergic reactions to food, pain killers (such as aspirin or arthritis tablets like naproxen, diclofenac) or antibiotics can also trigger hives. Sometimes insect stings, food additives or preservatives can trigger hives. Stress can certainly make established symptoms worse, but is a very rare cause of urticaria.

Most people with urticaria do not need tests

Tests are sometimes done when hives go on for long periods or when unusual symptoms are occurring around the same time. This is to exclude other diseases, which may appear as hives first and other conditions later. Allergy testing is performed when the history suggests of an allergic cause.

Angioedema can occur on its own

Angioedema occurs in around 1 in 3 people with hives. Angioedema is not always itchy and can sometimes be painful. Sometimes it can occur on its own. As well as in infection and allergy, angioedema is also seen in two other situations. Around 1 in 100 people taking heart/blood pressure medicines called ACE (Angiotensin Converting Enzyme) inhibitors will develop angioedema.

The tendency to angioedema can be inherited

Hereditary angioedema occurs in around 1 in 100,000 people. Patients lack an effective enzyme (known as C1 esterase), which is associated with non-itchy swellings of the face, throat or limbs. Swelling of the gut is a common symptom, resulting at times in severe abdominal pain.

Most hives are short-lived

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. Fortunately, that is the exception rather than the rule!

Treatment of urticaria and angioedema

• Time is a wonderful healer. Most resolve within a couple of weeks.
• Avoid aggravating factors. Non-specific measures such as avoiding excessive heat, spicy foods or alcohol are often useful.
• Aspirin should also be avoided as it often makes symptoms worse.
• Medication. Medicines like antihistamines are often used to reduce the severity of the itch. Severe throat swelling requires early use of medication and attention by your doctor or in hospital. Other medicines (like cortisone tablets) may be needed if symptoms are severe.
• Special diets. Occasionally, going on a restricted diet will help. Unfortunately, one cannot predict who will or will not respond to diet on the basis of history or allergy testing. The only way to sort it out is to put people on a temporary "elimination diet" under close supervision, followed by challenges if it helps.

It is important to note that information contained in this bulletin is not intended to replace professional medical advice. Any questions regarding a medical diagnosis or treatment should be directed to a medical practitioner.

References

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