Urticaria is another name for hives (or wheals). Hives are itchy, raised patches on the skin that can vary in shape, size and colour. They can appear anywhere on the body, are often extremely itchy, and can also cause a burning or stinging sensation.

Individual hives clear within 24 hours, although the overall rash may last longer.

Many people with urticaria also experience skin swelling. This is called angioedema, and it most commonly affects the eyelids, lips, genitals, tongue, hands and feet.


Diagram showing the difference in symptom duration between chronic spontaneous urticaria and chronic inducible urticaria


What are the symptoms?

What are the symptoms? The main symptom of urticaria is an itchy, raised rash, which is often made worse by scratching. It appears suddenly and can affect any area of the skin. Angioedema occurs in the deeper layers of skin tissues and, as a result, is more likely to be painful than itchy. Angioedema often takes longer to clear than hives.

Hives may be flesh-coloured, pink or red, turning white when pressed, and can be many different shapes and sizes. Angioedema causes prominent swelling and areas of the face are commonly affected (i.e. lips and eyes). This can be disfiguring and cause distress. In 1–13% of urticaria cases, only angioedema is present.

Urticaria does not usually affect general health, but the rash’s appearance and the itch itself can be extremely distressing, especially when it lasts for long periods. However, as a rule, urticaria tends to improve and become less troublesome over time.

If marked angioedema develops, it can be very alarming and upsetting. If the swelling affects the mouth or throat it may result in swallowing difficulties or a choking sensation. However, it is important to emphasise that life-threatening breathing difficulties are extremely unlikely in the type of angioedema that can develop with chronic urticaria. This is in contrast to specific acute allergic reactions (e.g. peanut allergy), when dangerous angioedema of the throat can develop. Please talk to your doctor or nurse for more information.


Graphical illustration of the prevalence of chronic urticaria, chronic inducible urticaria and chronic spontaneous urticaria in the population


Cause of symptoms

The physical symptoms of urticaria are caused by raised levels of histamine, a chemical released from mast cells, a type of white blood cell within your immune system. Mast cells are abundant not only in the skin but also in tissues such as the tongue and lips. They are located close to blood vessels and contain high amounts of histamine and various other chemicals. When mast cells release histamine, the local blood vessels widen and increase blood flow to the area. Histamine also stimulates local nerves in the skin, causing the symptoms of itch and occasionally pain.

CSU is not caused by allergy. Unfortunately, the cause of the histamine release in CSU remains unknown, hence the term ‘chronic spontaneous urticaria.’


Cut-away illustration of the skin, with details on the causes of chronic urticaria




The most important step in making a diagnosis of chronic urticaria is to get a detailed account of the patient’s history, including:

  • Timing, frequency and duration of symptoms
  • Shape, size, distribution and associated symptoms of hives and/or swellings
  • Family and medical history, including allergies
  • Correlation with any triggers, including food, exercise and drug use
  • Work, hobbies, smoking habits and stress
  • Previous therapy and response to treatment

If no identifiable triggers are involved, ‘chronic spontaneous urticaria’ is the accepted medical diagnosis.

In the majority of patients with chronic urticaria, when the patient’s account of their symptoms is clear-cut, there is no particular need for blood tests or other investigations. A photograph of the hives and/or swelling can be helpful in confirming the diagnosis.

In a small number of patients, tests and further investigations may be necessary. Carrying out multiple allergy tests without indicators from the patient’s history may not be appropriate. If allergy is suspected, blood or skin reaction tests can be performed; however, in the majority of patients, these tests are not warranted.



CSU is a chronic condition with an estimated duration of 1–5 years in most cases.

Diagram detailing the typical prognosis of chronic spontaneous urticaria from initial diagnosis up to 25 years




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XSU20-C026 July 2020.

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