What are the other Names for this Condition? (Also known as/Synonyms)

• ChU (Cholinergic Urticaria)
• Stress Urticaria
• Sweat Urticaria

What is Cholinergic Urticaria? (Definition/Background Information)

• Urticaria is a common inflammatory condition of skin that results in weals (red skin sign with itching) and/or angioedema (swelling due to fluid accumulation). It is seen in individuals of a wide age group and may be described as acute or chronic, based on the duration of the signs and symptoms
• Cholinergic Urticaria (ChU or CU) is a common form of urticaria that develops due to body temperature increase, caused by factors, such as participation in athletic sports, intense physical activities, or even following emotional stress/trauma
• Cholinergic Urticaria forms a subset of chronic inducible urticaria, a form of chronic urticaria, in which the signs and symptoms usually occur within a few minutes of exposure to the stimuli (or a known trigger)
• ChU is also known variously as Sweat Urticaria or Stress Urticaria and is more common among the younger population. This skin condition may arise following exercise, hot environments, or hot showers too, which leads to an elevation in one’s body temperature
• Due to increased stress or physical exertion, tiny red or white weals form on the exposed surfaces (neck and chest/back) that may present severe itching. Angioedema is reported in some cases of Cholinergic Urticaria
• In most individuals, the symptoms are mild and no treatment is necessary. In others with severe symptoms, the treatment may involve cooling the body, use of antihistamine medications, and immunosuppressive therapy
• The prognosis of Cholinergic Urticaria with adequate treatment is usually good, although the condition can recur. In a few individuals, complications including breathing difficulties, shock, and anaphylaxis may develop

Who gets Cholinergic Urticaria? (Age and Sex Distribution)

• Cholinergic Urticaria can affect both children and adults, though it is more often seen in teens and young adults in the age range 15-35 years (peak period noted is 26-28 years)
• It is a common skin condition that is reported to have a prevalence rate between 10-20% among older children, teenagers, and young adults (the age category that is affected the most)
• Both males and females are affected and no predilection for either sex is observed
• There is no race or ethnic preference noted

What are the Risk Factors for Cholinergic Urticaria? (Predisposing Factors)

The main risk factor for Cholinergic Urticaria is the presence of any condition that results in the elevation of one’s body temperature. This may occur from certain triggers including:

• Physical exercise/workouts causing profuse sweating
• Hot baths or showers, saunas
• Athletic sporting activities
• Hot environments caused by kitchens, working near industrial equipment that generate heat, working outdoors during hot sunny days, etc.
• Use of very thick jackets or winter clothing (trapping heat within the body)
• Emotional and psychological stress including excitement, fear, and anxiety, causing increased sweating

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Cholinergic Urticaria? (Etiology)

Urticaria can be caused by a variety of factors. The condition develops due to the release of chemical substances, such as histamines, platelet activating factor, and cytokines (example bradykinin), from inflammatory cells called mast cells and basophils.

• Cholinergic Urticaria is a form of physical urticaria that occurs following a known trigger, which is a rise in body temperature in this case. In many cases, the exact cause is unidentified (idiopathic Cholinergic Urticaria), though the trigger is mostly identified
• Scientific researchers have placed forward several proposals explaining the development of this form of skin condition
  • Some believe that Cholinergic Urticaria is related to aquagenic urticaria and the body releases histamine as an immune response, when sweat (water) reacts with the oily substances called sebum from sebaceous glands, to form certain allergic compounds
  • It is also reported that some individuals lack the ability to sweat normally (a condition called anhidrosis), or have a decreased ability to sweat following stressful environment or exercises (known as hypohidrosis) that leads to elevated body temperatures
• It is reported that individuals who are prone to ChU have a hereditary predisposition to certain allergic conditions (atopic diseases), such as asthma, hay fever, and lichen simplex chronicus (neurodermatitis), in nearly 50% of the cases

Most cases are known to occur randomly (sporadically); although, infrequently, a family history of the condition has been reported in the medical literature.

What are the Signs and Symptoms of Cholinergic Urticaria?

The signs and symptoms of Cholinergic Urticaria may be mild or severe, localized or diffused, and can vary from one individual to another. Mild symptoms (observed in a great majority of individuals) may not even be recognized by the affected individual. It may be perceived as sweat-related (or stress-related) discomfort and itching/burning of skin.

The signs and symptoms of Cholinergic Urticaria that occur within a few minutes to 20 minutes of sweating may include the following:

• Burning sensation and itching of the skin initially
• Formation of skin rashes or weals (wheals) that are associated with redness (or pinkish discoloration) and intense to severe itching
• Pain, pain on touch
• The symptoms are noted in the areas of sweat that usually begins with the neck, shoulders, and upper torso. When the condition is severe, the entire body may be affected
• The skin surrounding the affected area (weal) may be normal skin color or appear red (erythema)
• The weals may change in shape and size, but typically last for a short duration only
• The symptoms are known to subside when the stimulus ceases and the body returns to normal temperature
• Individual weals may vary in size, but are usually only a few mm in size (pin-points); numerous weals covering a large area of the body skin may be observed
• When pressure is applied on the affected area, it blanches (becomes pale or white in color)
• Scratching can result in worsening of the symptoms and lead to further skin complications such as ulceration and secondary infections
• Angioedema: It is the swelling due to fluid accumulation in the mucus membranes or deep within the skin. It is rarely observed with ChU

Occasionally, systemic symptoms including nausea and vomiting, gastrointestinal symptoms (diarrhea and stomach pain), breathing difficulties, and shock due to cardiovascular collapse, may be noted.

How is Cholinergic Urticaria Diagnosed?

Cholinergic Urticaria may be misdiagnosed as other forms of physical urticaria including aquagenic urticaria, hot/cold urticaria, exercise urticaria, or even sunlight urticaria. Hence, a careful examination by the healthcare provider is necessary.

A diagnosis of Cholinergic Urticaria may involve the following tests and examinations:

• Physical examination of the skin and medical history evaluation
• Radioallergosorbent (RAS) test; to determine the specific allergy-causing substance
• Skin allergy test using injection of sweat from the individual’s own body (autologous)
• Exertion test, which may be conducted by making the individual perform activities involving physical exertion, such as riding a stationary bicycle, stair climbing, or even taking a hot bath, in a controlled manner
• Blood test to detect various antibodies against allergens including:
  • Complete blood count (CBC) including eosinophil count since, there may be increased number of eosinophils (peripheral eosinophilia)
  • Antinuclear antibody (ANA) test
  • Erythrocyte sedimentation rate (ESR) test
  • Immunoglobulin E (IgE) levels in blood
  • Serum level of complement
  • Serum C-reactive protein blood test
• Tests to rule-out other underlying autoimmune conditions and infections (if necessary)
• Physical hot and/or cold provocation test
• Skin biopsy: A skin biopsy is performed and sent to a laboratory for a pathological examination. The pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis
• A differential diagnosis may be considered to eliminate certain skin conditions, prior to arriving at a definitive diagnosis

Note:

• The controlled exertion test is generally performed after a time lapse of at least 24 hours after the previous or last episode of Cholinergic Urticaria; otherwise, it may indicate a false-negative report
• The healthcare provider may induce symptoms by administering the triggers in a controlled fashion. This procedure is performed under close medical supervision, either in an out-patient healthcare setting, or as an in-patient setting in a hospital. Since, potentially life-threatening symptoms may develop during this procedure, access to emergency medical resources is generally warranted. Hence, such testing should not be performed at home

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Cholinergic Urticaria?

The following complications of Cholinergic Urticaria may be noted:

• Intense scratching may result in skin scarring
• Itching can lead to ulceration of skin, causing superimposed bacterial and fungal skin infections
• Severe cases can cause disruption in sleep
• Severe intolerance to heat
• Cosmetic concerns leading to stress
• Severe respiratory difficulties and cardiovascular shock may be infrequently observed
• The performance of sports professionals may be severely affected
• Frequent episodes of urticaria can affect the quality of life, which can result in severe stress. This severe stress can in-turn be a trigger for further worsening of the condition
• Involvement of the larynx due to angioedema, may be life-threatening and a medical emergency. If the larynx is involved, it can result in sudden breathing difficulties, due to laryngeal edema
• Severe ChU can result in anaphylactic shock, which is a potentially life-threatening medical condition

How is Cholinergic Urticaria Treated?

The treatment depends upon the severity of the signs and symptoms of Cholinergic Urticaria. In severe cases, an allergy specialist may be consulted. The treatment measures may include:

• Cooling the skin using moist towels, cold water sprays, air-cooled atmospheres; steps to bring the body temperature to normal levels
• Topical steroid treatment that may include moisturizing creams to soothe the condition
• Systemic steroids, if necessary
• Desensitization using autologous sweat (sweat from the patient), in some cases
• Anti-histamine therapy is generally known to be effective
• Use of mast cell stabilizers, anti-cholinergic medications (that may have certain side effects) 
• Immunosuppression therapy for severe symptoms: Use of immune modulators or medications that modulate immunity
• Patient education in understanding the condition is beneficial
• Some patients may be advised to use self-administered epinephrine injections, for anaphylactic shock or when indicated (such as before a sporting activity)
• Stress management for severe and chronic conditions

How can Cholinergic Urticaria be Prevented?

Although Cholinergic Urticaria may not be prevented, further and future flare-ups may be avoided, if the triggers that cause the condition are recognized and avoided.

• One may potentially control flare-ups or severe symptoms by undertaking milder exercises or performing any physical activity in a controlled fashion
• Avoiding triggers such as hot environments and hot baths/showers

What is the Prognosis of Cholinergic Urticaria? (Outcomes/Resolutions)

• The prognosis of Cholinergic Urticaria is generally good following removal of the triggering factor (increase in body temperature). In most cases, the skin condition resolves on its own within an hour (the weals disappear)
• In some cases, treatment may be necessary, and the prognosis is typically good with adequate treatment. However, the condition may recur
• Anaphylactic reaction/shock can be fatal without treatment
• It is observed in some individuals that Cholinergic Urticaria tends to get better after a few decades and the condition may altogether disappear

Additional and Relevant Useful Information for Cholinergic Urticaria:

Please visit our Skin Care Health Center for more physician-approved health information:

http://www.dovemed.com/healthy-living/skin-disorders/