Idiopathic Urticaria: What It Is and What Types Exist

Urticaria is a group of diseases in which itchy wheals appear on the skin, sometimes together with angioedema. The diagnosis of "idiopathic" is made when the external cause of the rash cannot be established. Below is information on how such cases differ from the rest and what forms of urticaria are distinguished today.

What idiopathic urticaria is

A wheal in urticaria is a flatly raised pale pink formation that itches intensely and resembles a nettle sting in appearance; it can appear anywhere on the body. The mechanism is linked to mast cells, which release histamine: the skin swells and itches. "Idiopathic" means that the cause cannot be established; in the classification it is called spontaneous (idiopathic).

Chronic urticaria is divided into spontaneous and inducible. The spontaneous form is called idiopathic because it is triggered by unknown external factors, and in 55% of patients the mechanism remains unexplained. Chronic spontaneous urticaria accounts for two thirds of chronic urticaria cases; the peak incidence is at age 20–40, and women are affected twice as often as men.

Acute and chronic urticaria: what the difference is

The boundary between the forms is temporal. Urticaria is considered acute when wheals and angioedema persist for less than six weeks; if the rash continues longer, the form is called chronic. In most people the rash resolves on its own within a few days.

Urticaria is very common: its various variants are diagnosed in 15–25% of people, and one in three experiences it at least once in their lifetime. A quarter of cases are chronic, and adults are affected more often than children. In adults the disease lasts on average from 3 to 5 years, angioedema is recorded in one in two, and the impact of symptoms on quality of life is comparable to that of psoriasis or coronary heart disease.

Inducible urticaria and other forms

Inducible urticaria develops upon exposure to physical stimuli — cold, heat, vibration, pressure. Delayed pressure urticaria manifests as swelling at the site of pressure, which develops several hours after exposure. One patient may have two or more forms, and a combination of spontaneous and inducible occurs in 13.9% of cases.

Rashes in urticaria vary in shape and size and can appear on any part of the body. Pigmentary urticaria in mastocytosis, urticarial vasculitis, and familial cold urticaria are today considered separately from urticaria.

Autoimmune, viral, and pigmentary urticaria: the link to causes

The autoimmune concept is discussed as an explanation for chronic spontaneous urticaria. In 45% of such patients, autoantibodies of the IgG and IgE classes are detected: IgG to immunoglobulin E — in 5–10%, IgG to the high-affinity IgE receptor on mast cells — in 35–40%. IgE-class antibodies to autoallergens are found in 33–52% of patients, with thyroid peroxidase and double-stranded DNA among the targets.

Among the causes cited are an allergic reaction to medications and food, as well as infections and stress; urticaria occurs more often in people with other allergies. Parasites, contrary to popular belief, turn out to be a rare cause of chronic urticaria, and the pigmentary form is associated with mastocytosis. Infections are among the causes of urticaria, but it is not distinguished as a separate "viral" form.

When to see a doctor

Urticaria usually resolves on its own, but some situations require prompt medical assessment.

• symptoms do not improve within two days;
• the rash spreads;
• the rash returns again;
• there is swelling under the skin — possible angioedema;
• high fever and general malaise.

If you are worried about a child, that is a reason to see a doctor.

Urticaria by itself is not a reason to call an ambulance; you should call 103 or 112 if the lips, mouth, throat, or tongue suddenly swell, breathing becomes rapid or difficult, wheezing and a feeling of suffocation appear, the throat tightens and swallowing is difficult, and the skin, tongue, or lips turn blue, gray, or pale.

This material is for reference: it describes the forms and signs of urticaria but does not replace consultation with a doctor, who will assess the specific situation.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer