Urticaria is a relatively common skin problem characterised by raised bumps, which are usually itchy and may be intensely uncomfortable. The bumps are often referred to as ‘hives’ but the name urticaria is derived from the resemblance to the rash caused by stinging nettles (urtica = nettle in Latin). Although the individual hives usually last less than a few hours, patients may be affected by recurring hives for days, weeks or longer. A bout of urticaria lasting less than 6 weeks is said to be ‘acute’, and urticaria lasting longer than 6 weeks is termed ‘chronic’.
In most cases of simple urticaria, the hives occur because a type of immune cell (known as a ‘mast cell’) in the skin releases histamine causing itching, redness and swelling. This is similar to what happens during an allergic reaction and therefore urticaria is often mistaken for allergy, although the differences will usually be apparent to a specialist doctor.
Ongoing urticaria is in fact rarely caused by allergy and the reason why mast cells release histamine is poorly understood. In some cases physical triggers such as exercise may provoke hives. Some people with urticaria may also experience swellings known angioedema – most commonly affecting the lips or eyes – that can last a few days.
For most people, urticaria will be a transient problem and does not indicate any other underlying physical illness. In many cases extensive tests are unnecessary and management is mainly aimed at minimising the impact of symptoms on daily life. The main approaches to treatment are use of antihistamines – often at higher dosages than used to treat allergy – and sometimes in combination with other anti-allergic treatments such as montelukast. For severe cases of chronic urticaria that do not respond to such measures, a monthly injection medication (omalizumab) has recently been approved by the UK National Institute for Health and Care Excellence (NICE).