Hives

Urticaria is a medical condition which is characterised by a presence of hives (weals) or angioedema.

A weal refers to a superficial pale or skin-coloured swelling which is usually surrounded by redness (erythema) that can remain active for a few minutes or an entire 24 hours. The swelling is typically itchy and may carry a burning sensation.

Angioedema refers to a much deeper swelling in the skin and can be skin-coloured or red. It usually lasts up to 72 hours and is often reported to be asymptomatic, though it may sometimes be painful or itchy.

Urticaria is classified into two types based on duration. Acute urticaria lasts less than six weeks. Chronic urticaria lasts more than six weeks with constant onsets of weals.

One in five individuals, regardless of age and sex, experiences an episode of acute urticaria at least once in a lifetime. Chronic urticaria affects approximately 0.5 to 2% of the entire population. Genetic and autoimmune predispositions are commonly observed.

Urticaria weals can range from just a few millimetres to several centimetres in diameter. The colours typically appear white or red, and the shape can be round or in the form of patches, rings, or map-like patterns. Any body site can be affected.

Angioedema tends to be more localised. It usually affects the face (eyelids and perioral sites), hands, and feet. In some cases, the tongue, larynx, or soft palate may be affected as well.

Assessment

Urticaria is assessed according to the visual analogue scale. Scores range from 0 to 3, with 0 representing no itch and no weals, and 3 representing more than 50 weals in the past 24 hours with intense itch. The emotional impact is also assessed in patients with urticaria. The Dermatology Life Quality Index (DLQI) is a specific questionnaire developed to assess chronic urticaria, with factors such as sleep disruption being evaluated.

Causes

Hives arise as a result of chemical mediators being released from circulating basophils and mast cells. These mediators, including cytokines, platelet-activating factor, and histamine, activate the sensory nerves, causing dilation of blood vessels and fluid leakage into adjacent tissues. The release of bradykinin causes angioedema.

Acute urticaria can be induced by various factors, including drug allergies (such as antibiotics) and food allergies (such as shellfish, peanuts, milk, and eggs). Bee and wasp stings may also be a cause.

The cause of chronic urticaria remains unknown; however, autoimmune factors are believed to be the primary cause. Other triggering factors include viral infection, tight clothing, heat, food pseudoallergy, and drug pseudoallergy.

Diagnosis

Urticaria is diagnosed in individuals who present a history of hives lasting less than 24 hours, with or without angioedema. Family history is evaluated as part of the assessment.

Skin prick tests or radioallergosorbent tests (RAST) may be requested to determine the presence of a food or drug allergy.

Treatment

The primary treatment for all forms of urticaria is an oral second-generation antihistamine. The standard dose is typically 10 mg. If this dose becomes ineffective, it may be increased to 40 mg. These medications are discontinued once acute urticaria resolves.