Summary about Disease
Cholinergic urticaria (CU) is a type of physical urticaria triggered by an elevation in body temperature that occurs due to physical exertion, emotional stress, or passive warming. It is characterized by the rapid appearance of small, intensely itchy wheals (hives) surrounded by redness (erythema).
Symptoms
Small, pinpoint-sized wheals (1-3 mm in diameter).
Intense itching (pruritus).
Redness (erythema) surrounding the wheals.
Wheals typically appear on the upper chest, neck, and arms, but can occur anywhere on the body.
Symptoms are often accompanied by systemic symptoms such as sweating, salivation, abdominal cramps, diarrhea, and headache in severe cases.
Causes
The exact cause of cholinergic urticaria is not fully understood. However, it is believed to be triggered by the release of acetylcholine, a neurotransmitter that stimulates sweat glands. This release is triggered by factors that increase body temperature, such as:
Exercise
Sweating
Hot baths or showers
Emotional stress
Spicy foods
Increased room temperature
Medicine Used
Antihistamines: The primary treatment for cholinergic urticaria. Non-sedating H1 antihistamines (e.g., cetirizine, loratadine, fexofenadine) are typically used first-line. Higher doses may be required.
H2 Antihistamines: (e.g., ranitidine, cimetidine) are sometimes used in combination with H1 antihistamines, but not as effective by themselves.
Omalizumab: An injectable biologic medication that may be considered for severe, refractory cases. It blocks IgE, reducing mast cell activation.
Beta-adrenergic antagonists: (e.g. Propranolol) Some patients get relief.
Epinephrine: Rarely needed unless there are systemic symptoms that constitute anaphylaxis.
Is Communicable
No, cholinergic urticaria is not communicable. It is not contagious and cannot be spread from person to person.
Precautions
Avoid triggers: Identify and avoid activities or situations that trigger outbreaks, such as intense exercise, hot environments, or stressful situations.
Cooling measures: Use cooling techniques, such as applying cool compresses, taking cool showers, or using fans, to help prevent or alleviate symptoms.
Loose clothing: Wear loose-fitting, breathable clothing to help prevent overheating.
Medical alert: If you have severe reactions, consider wearing a medical alert bracelet.
How long does an outbreak last?
An outbreak of cholinergic urticaria typically lasts from 30 minutes to 2 hours after exposure to the triggering stimulus. The wheals and itching usually resolve spontaneously within this timeframe.
How is it diagnosed?
Medical history and physical exam: The doctor will ask about your symptoms, triggers, and medical history.
Exercise challenge test: The patient exercises to induce symptoms.
Methacholine skin test: Involves injecting a small amount of methacholine, a cholinergic agent, into the skin to see if it triggers a reaction.
Timeline of Symptoms
Within minutes of trigger exposure: Itching and a warm sensation develop.
Within 5-15 minutes: Small wheals appear, surrounded by redness.
30 minutes to 2 hours: Symptoms peak and then gradually subside.
After a few hours: The skin returns to normal.
Important Considerations
Severity: Cholinergic urticaria can range from mild to severe. In severe cases, systemic symptoms like breathing difficulty or dizziness may occur, requiring immediate medical attention.
Coexisting conditions: People with asthma or other allergic conditions may be more likely to experience severe reactions.
Quality of life: Cholinergic urticaria can significantly impact quality of life due to the discomfort and limitations it imposes on physical activities.
Tolerance: Some individuals may develop tolerance to their triggers over time with repeated exposure. However, this is not a guaranteed outcome.