Author and DermNet NZ Editor-in-Chief: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand, January 2015.
Urticaria is a skin condition characterised by weals (hives) or angioedema (swellings, in 10%) or both (in 40%). There are several types of urticaria.
Chronic urticaria is urticaria in which there are daily or episodic weals or angioedema that is present for more than 6 weeks. Chronic urticaria may be spontaneous or inducible. Both types may co-exist.
Inducible or physical urticaria is classified according to the stimulus that provokes wealing.
Chronic spontaneous urticaria affects 0.5–2% of the population; in some series, two-thirds are women. Inducible urticaria is more common than spontaneous chronic urticaria. There are genetic and autoimmune associations.
Urticaria is characterised by weals.
Angioedema is more often localised.
In chronic inducible urticaria, weals appear about 5 minutes after the stimulus and last a few minutes or up to one hour. Characteristically, weals are:
The weals are more persistent in chronic spontaneous urticaria, but each has gone or has altered in shape within 24 hours. They may occur at certain times of the day.
Visual analogue scales can be used to record and compare the degree of itch.
The activity of chronic urticaria can be assessed using the UAS7 scoring system. The daily weal/itch scores are added up for 7 days; the maximum score is 42.
The emotional impact of urticaria and its effect on quality of life should also be assessed. The Dermatology Life Quality Index (DLQI) and CU-Q2oL, a specific questionnaire for chronic urticaria, have been validated for chronic urticaria, where sleep disruption is a particular problem.
Some patients with chronic spontaneous urticaria report associated systemic symptoms. These include:
Weals are due to release of chemical mediators from tissue mast cells and circulating basophils. These chemical mediators include histamine, platelet-activating factor and cytokines. The mediators activate sensory nerves and cause dilation of blood vessels and leakage of fluid into surrounding tissues. Bradykinin release causes angioedema.
Several hypotheses have been proposed to explain urticaria. The immune, arachidonic acid and coagulation systems are involved, and genetic mutations are under investigation.
Chronic spontaneous urticaria is mainly idiopathic (cause unknown). An autoimmune cause is likely. About half of investigated patients carry functional IgG autoantibodies to immunoglobulin IgE or high-affinity receptor FcεRIα.
Chronic spontaneous urticaria has also been associated with:
Weals in chronic spontaneous urticaria may be aggravated by:
Inducible urticaria is a response to a physical stimulus.
Chronic urticaria is diagnosed in people with a long history of daily or episodic weals that last less than 24 hours, with or without angioedema. A family history should be elicited. A thorough physical examination should be undertaken to evaluate the cause. Inducible urticaria is often confirmed by inducing the reaction, eg, scratching the skin in dermographism or applying an ice cube in suspected cold urticaria.
There are no routine diagnostic tests in chronic spontaneous urticaria apart from blood count and C-reactive protein (CBC, CRP), but investigations may be undertaken if an underlying disorder is suspected.
The main treatment for chronic urticaria in adults and in children is with an oral second-generation antihistamine chosen from the list below. If the standard dose (eg 10 mg for cetirizine) is not effective, the dose can be increased fourfold (eg 40 mg cetirizine daily). There is not thought to be any benefit from adding a second antihistamine.
Although systemic treatment is best avoided during pregnancy and breastfeeding, there have been no reports that second-generation antihistamines cause birth defects. If treatment is required, loratadine and cetirizine are currently preferred.
Conventional first-generation antihistamines such as promethazine or chlorpheniramine are no longer recommended for chronic urticaria:
In addition to antihistamines, the triggers for urticaria should be avoided where possible. For example:
The physical triggers for inducible urticaria should be minimised; see examples below. However, symptoms often persist.
Patients with chronic urticaria that has failed to respond to maximum-dose second-generation oral antihistamines taken for 4 weeks should be referred to a dermatologist, immunologist or medical allergy specialist.
Other treatments that are sometimes used off-label in chronic urticaria include:
Long-term systemic corticosteroids are not generally recommended, as high doses are often required to reduce symptoms of urticaria and they have inevitable adverse effects that can be serious. However, a study published in 2018 has reported effective clearance and long-lasting response of chronic spontaneous urticaria to oral prednisolone.
Although chronic urticaria clears up in most cases, 15% continue to have wealing at least twice weekly after 2 years.
Vas K, Altmayer A, Mihályi L, Garaczi E, Kinyó Á, Jakobicz E, Husz S, Kemény L, Bata-Csörgő Z. Successful Treatment of Autoimmune Urticaria with Low-Dose Prednisolone Therapy Administered for a Few Months: A Case Series of 42 Patients. Dermatology. 2018 Jan 17. doi: 10.1159/000484085. [Epub ahead of print] PubMed PMID: 29339636.
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