eMedicine Specialties > Dermatology > Allergy & Immunology

Urticaria, Cholinergic

Author: Robert A Schwartz, MD, MPH, Professor and Head, Dermatology, Professor of Pathology, Pediatrics, Medicine, and Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School
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Updated: Jul 1, 2009

Introduction

Background

Cholinergic urticaria is one of the physical urticarias brought on by a physical stimulus. Although the physical stimulus might be considered to be heat, the actual precipitating cause is sweating.

Additional eMedicine articles on urticaria, including Urticaria, Acute; Urticaria, Chronic; Urticaria, Contact Syndrome; Urticaria, Dermographism; Urticaria, Papular; Urticaria, Pressure; and Urticaria, Solar, may be of interest.

Pathophysiology

Mast cells seem to be critically involved; cholinergic urticaria has been used to study mast cell activity.¹ Serum histamine, the principal mediator, rises in concentration with experimentally induced exercise, accompanied by eosinophil and neutrophil chemotactic factors and tryptase. A reduction of the alpha 1-antichymotrypsin level, as seen in some other forms of urticaria, is present, and the eruption is improved with danazol. These findings have prompted some to argue for proteases as a cause of histamine release.

Although mast cell release seems to be involved in cholinergic urticaria, less eosinophilic major basic protein is present than in many other forms of urticaria.

Several factors, including an increased incidence in patients with atopic dermatitis (AD), a marked sensitivity in some patients with anaphylactic and anaphylactoid reactions, and an immediate reactivity in some patients, suggest an allergic basis for cholinergic urticaria. One report showed positive immediate sensitivity to sweat with passive transfer. Some investigators, but not others, have reported positive passive transfer. Another group has reported a follicular pattern of cholinergic urticaria in sweat-sensitized patients but not in patients without prominent sensitivity. Patients with AD and cholinergic urticaria both develop skin reactions and histamine release of basophils in response to autologous sweat.²

Autonomic functions are normal in cholinergic urticaria. One patient with cholinergic urticaria developed an accentuated response in a positive copper test site, perhaps from either vasodilatation or augmentation of neurologic stimulation. In one study of cholinergic urticaria, muscarinic receptors were reduced, but binding was normal. Thermography ostensibly shows the areas of involvement.

Elevation of histamine levels can be detected at 5 minutes after exercise, reaching a peak of 25 ng/mL at 30 minutes in persons with cholinergic urticaria. Treadmill exercise produces a sensation of generalized skin warmth, followed by pruritus; erythema; urticaria; and transient respiratory tract symptoms consisting of shortness of breath, wheezing, or both. Statistically significant decreases were observed in 1 second forced expiratory volumes, maximal midexpiratory flow rates, and specific conductance. An increase in residual volume was also detected.

Frequency

United States

The prevalence of cholinergic urticaria is variable. Moore-Robinson and Warin³ found that about 0.2% of patients in an outpatient dermatologic clinic had cholinergic urticaria. However, many published series have found cholinergic urticaria to be common. The prevalence of cholinergic urticaria is definitely higher in persons with urticaria; cholinergic urticaria affected 11% of a population with chronic urticaria in one study, and 5.1% of persons with urticaria in another study. The prevalence is higher in persons with atopic conditions (eg, asthma, rhinitis, atopic eczema), but this is by no means exclusive. A rare familial form of cholinergic urticaria is also reported.

Sex

Cholinergic urticaria occurs in both men and women, but it seems to be more common in men than in women.

Age

• Cholinergic urticaria usually begins in people aged 10-30 years, with an average age at onset of 16 years in one study and a mean age of 22 years in another study. Cholinergic urticaria persists for a number of years. Most patients retain the tendency for many years.
• In one series of 22 persons, the average duration of cholinergic urticaria was 7.5 years, with a range of 3-16 years, but, in 7 patients on follow-up study, some patients retained the cholinergic urticaria tendency for 30 years.
• In another study, almost 96% of patients with cholinergic urticaria were men, with a mean age of 22 years, whereas in another group, 31 women and 25 men had cholinergic urticaria.

Clinical

History

• Cholinergic urticaria lesions appear rather rapidly, usually within a few minutes after the onset of sweating, and they 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.
  • 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,⁴ 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.

Physical

• 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 Media File 1).

• 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.⁵
  • Superficial obstruction of the acrosyringium has sometimes been associated with acquired generalized hypohidrosis.⁶

Causes

• 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.

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