Chronic spontaneous urticaria: long-lasting hives explained

Urticaria, also called hives, causes highly itchy raised patches on the skin known as weals. The British Association of Dermatologists (BAD) says they may be round or ring-shaped, may join together, can appear anywhere on the skin, and typically disappear of their own accord within 24 hours. Spontaneous urticaria is divided into acute, lasting up to six weeks, and chronic, lasting six weeks or more.

Primary care dermatology guidance (the Primary Care Dermatology Society, PCDS) adds that chronic urticaria is defined by symptoms lasting more than six weeks, and that 95 per cent of it is spontaneous, meaning there is no obvious cause or trigger. The rest is chronic inducible urticaria, where something such as cold or pressure sets off the weals. PCDS also notes that many people with CSU have some inducible element too.

The main symptom is itch. PCDS describes weals that last minutes to hours, generally resolving within 24 hours, appearing randomly and seeming to move from one area to another each time they come and go. On skin of colour, weals may look violaceous, hyperpigmented or the same colour as the surrounding skin, which can make them harder to spot.

Urticaria can occur with or without angioedema, which is swelling deep to the skin. BAD says angioedema usually affects soft areas such as the eyelids, lips or inside the mouth, tends to be painful rather than itchy, and takes longer to clear. PCDS says angioedema in CSU is never life-threatening in the way anaphylaxis is. BAD says swelling of the tongue or throat can be alarming but is only life-threatening when it is due to hereditary angio-oedema or an ACE inhibitor medicine.

BAD explains that urticaria is caused by the release of histamine and other chemicals from mast cells in the skin. In chronic spontaneous urticaria the process may be autoimmune, involving the person's own antibodies, although BAD says tests for autoimmune urticaria are not routinely available and generally do not alter treatment. When no cause can be found it is called idiopathic.

PCDS describes CSU as a mast cell condition in which histamine causes swelling and itch, and says it is not an allergy. Symptoms can however be made worse by heat, stress, alcohol, and medicines such as aspirin and other anti-inflammatory painkillers. BAD says some people with urticaria also have thyroid disease or other autoimmune conditions.

• Heat, tight clothes and alcohol can aggravate weals (BAD).

• Aspirin, ibuprofen and other non-steroidal anti-inflammatory drugs may worsen urticaria, and so may opiates such as codeine (BAD, PCDS).

• ACE inhibitors, used for high blood pressure, can cause angioedema without weals (BAD).

• In a small proportion of people, foods, colourings and preservatives appear to worsen it, and a food diary can sometimes help identify them (BAD).

BAD says the appearance, or a description of it, is usually enough for a diagnosis. There is no special test that can reliably identify the cause, most people who respond well to antihistamines do not need any tests, and routine allergy tests are not necessary. PCDS agrees that CSU is a clinical diagnosis, that blood tests are not routinely required, and that skin prick tests and patch testing have no place.

Specialists may sometimes check a full blood count, ferritin, thyroid antibodies or total IgE in secondary care to help plan treatment, but PCDS says a link between iron deficiency and CSU has not been corroborated in larger trials, and that a causal link with thyroid dysfunction has not been found. If you suspect a medicine has triggered urticaria, tell your doctor; BAD notes that a Yellow Card report can be made to the MHRA.

BAD says the aim of treatment is to suppress symptoms until the condition improves naturally, rather than to cure it. PCDS describes a stepped approach. These are prescription-level decisions that need a clinician who knows your history, so the table is a description rather than a guide to self-treating.

BAD says oral steroids can occasionally be used as rescue treatment for severe flares but are generally unnecessary because side effects usually outweigh benefits. It also describes H2 antihistamines, normally used for stomach acid, as something that can be added when standard antihistamines are not enough, whereas PCDS states there is no role for first-generation antihistamines or H2 antihistamines in CSU. This kind of difference is a reason to discuss options with a clinician.

PCDS says treatment should continue at the lowest effective dose until there has been no activity for 12 weeks, and restarted if urticaria returns, and that second-generation antihistamines are generally safe to take for as long as needed. It also says that when using higher doses, other health conditions should be considered because some antihistamines are cleared by the kidneys and others by the liver.

BAD says urticaria generally has no direct effect on general health, but it can have a high impact on quality of life, including mood, and can lead to problems with work and relationships. PCDS gives a natural history in which most people have CSU for 1 to 4 years, with remission in about 17 per cent at 1 year, 50 per cent at 5 years and 73 per cent at 20 years, and relapse in around a third. The course in any one person is unpredictable. PCDS suggests symptom scores such as the Urticaria Control Test, and a symptom diary can help you and your clinician judge whether treatment is working.

The NHS says to call 999 if your lips, mouth, throat or tongue suddenly swell, if you are breathing very fast or struggling to breathe, if your throat feels tight or you cannot swallow, or if you become suddenly confused, drowsy or dizzy or someone faints and cannot be woken. These can be signs of a serious allergic reaction. The NHS also says to seek an urgent GP appointment or NHS 111 if hives do not improve after 2 days, keep coming back, or come with a high temperature and feeling unwell.

Most people with CSU are looked after by a GP, with dermatology or allergy referral when antihistamines do not control symptoms. Omalizumab is only available through specialist clinics, which can be NHS or private; ask how response will be judged and how long treatment is expected to continue.