Physical urticaria

A type of urticaria triggered by physical stimuli

Overview

Physical urticaria rash on the skin

Physical urticaria is a subset of urticaria, commonly known as hives, which is triggered by specific physical stimuli. These stimuli can include pressure, temperature changes, sunlight, water, vibration, and exercise. The condition is characterized by the rapid development of wheals or angioedema in response to these triggers.

Types of Physical Urticaria

Physical urticaria can be classified into several types based on the triggering stimulus:

Dermatographic Urticaria

Also known as dermatographism, this type occurs when the skin is stroked or scratched. The affected area becomes raised and inflamed, often forming a linear pattern.

Cold Urticaria

This type is triggered by exposure to cold temperatures, including cold air, water, or objects. Symptoms can range from mild hives to severe reactions, such as anaphylaxis, upon rewarming.

Cholinergic Urticaria

Triggered by an increase in body temperature, cholinergic urticaria is often associated with exercise, hot showers, or stress. It is characterized by small, itchy wheals surrounded by areas of redness.

Solar Urticaria

This rare form is triggered by exposure to sunlight. The reaction can occur within minutes of sun exposure and typically resolves quickly once the stimulus is removed.

Aquagenic Urticaria

A rare condition where contact with water, regardless of its temperature, causes hives. The mechanism is not well understood, but it is believed to involve a reaction to water-soluble antigens.

Pressure Urticaria

This type occurs after sustained pressure on the skin, such as from tight clothing or prolonged sitting. The reaction can be delayed, appearing several hours after the pressure is applied.

Pathophysiology

The underlying mechanism of physical urticaria involves the release of histamine and other inflammatory mediators from mast cells in the skin. This release is triggered by the specific physical stimulus, leading to the characteristic wheals and itching.

Diagnosis

Diagnosis of physical urticaria is primarily clinical, based on the patient's history and the physical examination. Provocation tests, where the suspected stimulus is applied to the skin under controlled conditions, can help confirm the diagnosis.

Management

Management of physical urticaria involves avoiding known triggers and using medications to control symptoms. Antihistamines are the mainstay of treatment, helping to reduce itching and wheal formation. In severe cases, other medications such as omalizumab or corticosteroids may be used.

Prognosis

The prognosis for physical urticaria varies depending on the type and severity. Some individuals may experience spontaneous resolution over time, while others may have persistent symptoms that require ongoing management.

Related pages

• Urticaria
• Dermatographism
• Anaphylaxis
• Histamine