The Sweat Question
While this type of reaction is usually cholinergic urticaria, Ostro allows that two studies have implied – not proved – that there may be an allergy to one of the components of sweat in a rare group of individuals. Still, there is little to support an actual “allergy to sweat” in medical case studies.
“Though this mechanism may be operating in a few individuals, researchers who study CU attribute the majority of cases to an abnormal response of the nervous system called the cholinergic nervous system,” he says.
Perspiration, however, can assist a breakout of contact dermatitis, by releasing allergens from clothing or towels or adding to dermatitis irritation. But to be clear: the sweat itself does not cause such hives.
Ostro stresses that cholinergic urticaria is “not a form of contact dermatitis.” Contact dermatitis doesn’t develop immediately, “but takes 48 hours after contact with the inciting substance before skin lesions develop.” Those welts also take days to resolve, not minutes or an hour as is usually seen with CU.
The heat-triggered cholinergic urticaria is one of the physical urticarias, which also include reactions to cold, sun, even (in rare instances) water. It is also the only form of hives that can be sparked by emotions, such as anger.
It’s important to note a separate and dangerous form of exertion reaction: exercise-induced anaphylaxis or EIAn. This is a condition in which anaphylaxis, the most severe form of allergic reaction, results when a susceptible person exercises. It can also occur during strenuous chores, such as shoveling snow.
Unlike cholinergic urticaria, EIAn is only triggered by exercise, not heat stimuli. The reaction starts within minutes of exercise with flushing, itching and half-inch or larger hives (unlike cholinergic urticaria’s tiny hives). If exercising continues, the reaction can progress to anaphylaxis with swelling (face, throat, fingers, toes), nausea, abdominal cramps, diarrhea and loss of blood pressure.
There’s a sub-type of EIAn that only occurs when exercising within two to four hours after eating a specific food. The individual can exercise without symptoms, as long as the incriminated food is not consumed beforehand. Likewise, the person can eat that food with no reactions as long as no exertion follows for more than four hours after eating the food.
This condition, known as Food-Dependent EIAn, is challenging to diagnose. If you suspect symptoms of this, be sure to see an allergist for testing.
In fact, Ostro recommends that individuals who start to experience flushing, itching or hives during exercise immediately stop the activity, and consult an allergist before resuming a workout regime. When EIAn is diagnosed, the person will be prescribed an epinephrine auto-injector.
“Cholingeric urticaria is bothersome but non-life threatening, while EIAn is a potentially life-threatening condition,” Ostro says. Fortunately, the former condition is the more prevalent.
So can the person with cholingeric urticaria hives stay fit and exercise? Yes, but it may involve finding a less heat-inducing sport such as swimming, or inclining to winter sports such as skiing.
Kavanagh, who lives in New Brunswick, Canada, enjoys both. But she doesn’t limit herself to them. She races dirt bikes and rappels off mountains, too. She just ensures that she takes appropriate safeguards to avoid and minimize her body heat reactions.
Besides staying out of direct sunlight and taking medication, Kavanagh layers her clothing for temperature changes, and wears a “cold” shirt that wicks away sweat while maintaining her active lifestyle. “I refuse to let my allergy get the best of me.”
First published in Allergic Living magazine.
To subscribe and get the magazine right at your door, click here.
© Copyright AGW Publishing Inc.