Individuals who end up with physical urticaria usually have a physical trigger for the hives such as cold, heat, pressure, sunlight, exercise or water. Some individuals with chronic urticaria usually have a physical cause. As for a heat rash or heat urticaria, this is considered as a chronic form of hives that is triggered by an increase in the body temperature.
Hives is triggered by any increase in the body temperature such as eating spicy foods, taking hot showers, engaging in strenuous exercises or using a lot of covers in bed at night. Even strong emotions can also instigate the development of hives among those who have cholinergic or heat urticaria.
The hives in this type of urticaria are distinctively pin-point in size usually less than the size of a mosquito bite. In some cases, they can clump together or coalesce into larger hives over time. Occasionally, the heat rash can be linked with severe symptoms including low blood pressure and asthma symptoms. Remember that the individual should not have exercise-induced anaphylaxis which is a severe allergic reaction linked with exercise. Individuals with cholinergic or heat urticaria often have hives once there is an increase in the body temperature such as a hot bath, not just exercise. In some individuals, it is not clear why this occurs, but some appear to be allergic to their own sweat. The condition is determined with skin testing using the sweat of the individual.
Diagnosing cholinergic or heat rash
The symptoms along with potential triggers that increase the body temperature are indicative of cholinergic or heat urticaria. In some circumstances, a variety of testing might be required to come up with an actual diagnosis. Some doctors will perform skin testing to methacholine which is a chemical that might instigate a positive test among individuals with cholinergic urticaria. It is sad to note that this test is only positive in some individuals who suffer from this syndrome.
Other testing measures include any method that can increase the body temperature of the individual including a hot water bath and exercise. Take note that these tests are not usually performed in most clinical settings and the diagnosis is typically done based on the history of the symptoms.
Treatment of heat rash
The suitable treatment for cholinergic or heat urticaria involves the use of antihistamines. Even though any antihistamine is usually beneficial, the older antihistamines such as hydroxyzine appear to work efficiently.
As for severe cases of cholinergic urticaria, they have been treated successfully with danazol which is an anabolic steroid. Just remember though that the use of this medication is limited due to its severe side effects.
Some individuals who have heat rash usually respond well to beta-blockers, particularly when strong emotions seem to be the cause of the symptoms of the individual. Take note that these medications must be used with care among individuals who might have exercise-induced anaphylaxis.