The most common leg rashes that occur from exercising are heat rashes and cholinergic urticaria. Considering the similarities between the symptoms of these two rashes, it may be difficult to determine which you are experiencing without a doctor's examination while exercising.
For both heat rash and cholinergic urticaria, an increase in body temperature or the precipitation of sweat is often the cause. A heat rash occurs when sweat ducts become blocked causing sweat to become trapped under the skin. Miliaria profunda, a form of heat rash, appears soon after exercising because of the increased amount of sweat associated with physical activity, according to MayoClinic.com. The cause of cholinergic urticaria occurs when the hypothalamus detects a temperature increase causing neurons to release acetylcholine, which assists in degranulation of mast skin cells that release histamines, according to CholinergicUrticaria.net. The histamines cause inflammation of the skin.
If a rash is present on your legs after exercising, you will feel itching, burning, tingling or a prickling feeling. You may experience a warm sensation on the rash and the appearance and feeling will worsen if you scratch the area. The rash can vary in severity. The skin may appear reddened and raised. An itch during or following exercising is the most common symptom of cholinergic urticaria, according to CholinergicUrticaria.net. If cholinergic urticaria is severe, heart palpitations, fainting, headaches, shortness of breath, wheezing, salivation, diarrhea and abdominal cramping can occur, according to DermNetNZ.
Both heat rash and cholinergic urticaria usually disappear on their own. In some cases, an oral anti-histamine or beta-blocker can help alleviate the symptoms, according to DermNetNZ. Lowering your body temperature by using an ice pack, cold wash cloth or air conditioning can improve the rash's condition.
Keeping your skin cool during and after exercising is the best way to prevent heat rash and cholinergic urticaria. Use the same methods you would use for prevention as you would for treatment of these rashes. While working out, wear moisture-wicking clothing, according to MayoClinic.com. Wear shorts instead of pants. Increase the frequency of times you work out because the more you exercise, the less severe your rashes will be, according to Cholinergic.Urticaria.net.
Most of these rashes will disappear within an hour after you exercise because your body temperature will naturally decrease. Contact your doctor if the rash begins to pus or your lymph nodes become swollen in the armpit, neck or groin, according to MayoClinic.com.