Urticaria

The name urticaria has originated from the famous European stinging nettle Urtica dioica. The condition is mainly characterised by the appearance of very itchy hives (weals) with or without the presence of adjacent erythematous flares. It can be either acute, inducible, or spontaneous.

A weal is defined as a superficial skin swelling which appears as skin-coloured or pale. It is usually surrounded by erythema that can last from a couple of minutes to an entire day.

Urticaria is classified into acute and chronic urticaria, depending on its duration. Acute urticaria lasts less than 6 weeks and usually disappears within a few hours to days. Chronic urticaria, which can be either inducible or spontaneous, lasts more than 6 weeks with daily or episodic occurrence of weals.

One in five children or adults will experience an episode of acute urticaria during their lifetime. All sexes are equally affected.

Acute urticaria can affect newborns and infants; however, these cases are quite rare. Acute urticaria is usually caused by infection in children. In older children, other factors such as medication, food, and inhaled allergens can trigger this condition. In adults, idiopathic and spontaneous urticaria is more prevalent.

Acute urticaria accompanied by fever can be the first sign of COVID-19 infection.

Chronic spontaneous urticaria (CSU) is more prevalent in women, accounting for 2/3 of all reported cases. Overall, 0.5 to 2% of the general population is affected.

In comparison with chronic spontaneous urticaria, chronic inducible urticaria is more common.

Urticarial weals have the following clinical features: they vary from a few millimetres to centimetres in diameter; they can be red or white; and they may or may not include a red flare. Weals may appear as giant patches, round formations, or rings.

Chronic spontaneous urticaria is assessed via the UAS7 scoring system. The daily weal and itch scores are added together over seven days, with a maximum awarded score of 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 are commonly used questionnaires for this purpose.

Weals are triggered by the release of chemical mediators, such as cytokines, histamine, and platelet-activating factor, from circulating basophils and tissue mast cells. These mediators stimulate sensory nerves and result in dilation of blood vessels and leaking of fluids into surrounding tissues.

Different hypotheses have been proposed to explain the causes of urticaria. Arachidonic acid, immune system, and coagulation systems are considered primary agents in triggering this condition. However, further studies are needed to determine which genetic mutations are responsible for causing urticaria.

Urticaria is diagnosed in patients who have a history of weals lasting less than 24 hours, with or without angioedema. Family history and history of medication use should be assessed, and a careful physical examination should be conducted.

If food, drug, or latex allergy is suspected in acute urticaria, the patient will be referred for additional tests such as skin prick tests and radioallergosorbent tests (RAST).

The primary treatment method for urticaria administered to adults and children is an oral second-generation H1-antihistamine, such as loratadine or cetirizine.

Generally, acute urticaria resolves within hours to days but can recur in the future. Chronic urticaria usually clears; however, in 15% of cases, wealing can be observed twice weekly after two years.