There is something I often hear in the clinic every summer: “It is hot when I go outside, cold when I come indoors, and then my skin suddenly heats up and becomes itchy.” It is easy to dismiss this as discomfort from being sensitive to heat, but it may be cholinergic urticaria, which reacts sensitively to changes in body temperature.
Signals the Skin Sends When Body Temperature Rises
Cholinergic urticaria tends to appear when internal body temperature rises relatively quickly. Common triggers include intense exercise, long hot baths, hot weather, and tension or stress. In summer, moving back and forth between strongly air-conditioned indoor spaces and hot outdoor environments can repeatedly stimulate the skin and autonomic nervous system.
Symptoms may include reddish wheals, stinging, a burning sensation, and itching. They may calm down for a while and then flare again in similar situations. Because the pattern can overlap with solar urticaria, which worsens with sunlight, or exercise-induced urticaria, which appears after exercise, it is important to look at the triggering situations together.
Too Much or Too Little Sweat Can Both Be a Problem
When I evaluate urticaria, I always check the amount of sweating and how sweating occurs. Sweat is an important body fluid that cools body temperature, washes the skin surface, and reflects the body’s circulation status. Excessive sweating can make the skin easily irritated, but if sweating does not occur well when it should, heat may remain inside and discomfort can increase.
In Korean medicine, skin conditions are assessed from the perspective of regulating sweating—that is, the secretion and release of sweat. The goal is not simply to make you sweat more, but to find a direction that also adjusts heat stagnation, dryness, swelling, and inflammatory responses according to your constitution and current condition.
Stress and Sleep Also Affect Skin Immunity
Some people have repeated urticaria even when external temperature stimulation is not strong. In these cases, we also need to look at factors that disturb the body’s internal balance, such as overwork, tension, anger, and lack of sleep. When the autonomic nervous system becomes sensitive and recovery declines, the skin may overreact even to small heat stimuli.
Treatment should not stop at briefly suppressing itching. It is necessary to plan care that helps restore the skin’s ability to process heat, regulate sweat, and stabilize inflammatory responses. If you are already taking prescription medication such as antihistamines, please do not stop it on your own and consult your medical team.
We Recommend a Consultation in These Cases
- When a stinging, itchy rash repeatedly appears whenever you exercise, shower, or stay in a hot place
- When urticaria continues for several weeks or longer, or the affected area spreads
- When you hardly sweat at all, or conversely, sweat excessively with even slight movement
- When skin symptoms worsen along with stress or sleep problems
- When your lips or throat swell, or you feel short of breath and dizzy, call 119 or go to the emergency room first
Summer urticaria may not be only a skin problem, but a signal involving body temperature regulation, sweat, and stress responses together. If symptoms repeat, I recommend recording your triggers and receiving care that also evaluates the body’s heat and circulation status.