Cholinergic Urticaria Clinical Presentation

Cholinergic urticaria lesions appear rather rapidly, usually within a few minutes after the onset of sweating, and last from a half-hour to an hour or more, with a mean duration of about 80 minutes.

Cholinergic urticaria symptoms are sufficiently uncomfortable to cause many patients to change their patterns of activity to prevent attacks.

Cholinergic urticaria symptoms seem to follow any stimulus to sweat. A crucial point in cholinergic urticaria is not the actual temperature of the skin surface, the average skin temperature, or even the core temperature, but it is an increase or a decrease in the weighted average body temperature. An increase in core body temperature may trigger for cholinergic urticaria; some patients appear unaffected by exercise and other activity in the summer.^[10] It has been suggested that 2 conditions are required to provoke seasonal cholinergic urticaria: heat provoked by various cholinergic stimuli and a low ambient temperature. Exploration of the relationship may be desirable. In cholinergic urticaria, whether skin lesions are provoked by passive heating of the body at rest (eg, saunalike conditions) or by active heating at a low ambient temperature is basically related to the thermoregulatory process.

Exercise is the most common precipitating event for cholinergic urticaria, but any activity that causes sweating, including elevated environmental temperature, hot food, sauna baths, immersion in hot water, gustatory stimuli, emotional stress, and hemodialysis,^[11] can bring on an urticaria attack in some persons.

Some persons who report cholinergic urticaria symptoms only during the winter months apparently have a reaction only when exposed to heat or heat-producing exercise while not acclimatized to heat.

Often in cholinergic urticaria, itching, burning, tingling, warmth, or irritation precedes the onset of numerous small (1-4 mm in diameter) pruritic wheals with large surrounding flares (see the image below).

Cholinergic urticaria lesions may appear anywhere on the body, except on the palms or the soles and rarely in the axillae. Sometimes, flares are the only presentation.

Patients who are more severely affected with cholinergic urticaria may experience systemic symptomatology, such as fainting, abdominal cramping, diarrhea, salivation, and headaches. Hepatocellular injury, angioedema, asthma, anaphylactoid, and even anaphylactic reactions are also reported. Persons with cardiorespiratory symptoms include patients with increased pulmonary resistance with acetylcholine challenge, which may be a limiting factor in certain occupations (eg, those relating to aerospace).

One form of cholinergic urticaria, sometimes called cholinergic erythema, is believed to show persistent and individual macules of short duration but with new macules continually appearing at adjacent sites.

Cholinergic dermographism comprises a localized distribution of typical tiny wheals that appear after stroking the skin of some patients with cholinergic urticaria.

A localized form of cholinergic urticaria and a presentation with cold-induced urticarial lesions may occur. Patients with this condition experienced a generalized reaction to cold ambient air and cold water (but a negative response to the ice-cube test). Cold urticaria and cold-induced cholinergic urticaria may be seen in about 1% of patients with cold urticaria.

Cholinergic urticaria may also occur in the setting of acquired forms of generalized absence or decrease in sweating. Some patients with acquired idiopathic generalized hypohidrosis are theorized to have a defect in the nerve-sweat gland junction.^[12] Superficial obstruction of the acrosyringium has sometimes been associated with acquired generalized hypohidrosis.^[13]

Of physical urticarias, cholinergic urticaria had the shortest course from onset to 50% remission, which was 34 months in one large series from an urticaria clinic.^[14]

Exercise and hot baths exacerbate pruritus and provoke lesions in previously unaffected areas.

Other diagnostic considerations for cholinergic urticaria are as follows:

• Some reports of chronic urticaria include patients with cholinergic urticaria, but the morphology is different. However, other physical urticarias with similar lesions, such as aquagenic urticaria, exist.
• Aquagenic urticaria appears in response to water at both cold temperatures and hot temperatures; when exposed to tap water at room temperature, the lesions resemble those of cholinergic urticaria.
• In adrenergic urticaria, wheals are surrounded by vasoconstriction, and the response to epinephrine and norepinephrine is positive.

Commonly, patients with one physical urticaria tend to have another physical urticaria as well, sometimes precipitated by the same stimulus.

Cholinergic urticaria may be accompanied by cold urticaria, pressure urticaria, and even aquagenic urticaria.