Any kind of itching or rash during running can be annoying and demoralizing. A rash on the buttocks could be caused by any of several dermatological irritants, environmental factors or underlying health problem. The benefits of regular exercise can outweigh the difficulties associated with a rash; talk to your doctor about preventative and treatment options for a running-induced rash.
Acne mechanica is a type of acne which most commonly occurs in a warm, moist environment — and particularly those areas experiencing forces of friction during exercise. Tight-fitting athletic apparel not made of breathable material can cause a flare-up of acne mechanica on a runner's buttocks area. You can reduce your risk of acne mechanica on the buttocks by opting for running shorts made of loose-fitting, moisture-wicking fabrics. If these preventative measures fail, prescription medications for acne mechanica are available.
If you are running in a hot or humid environment, it is possible to develop heat rash on the buttocks. Heat rash commonly occurs in hot and humid weather, when sweat ducts get blocked and your perspiration cannot escape through your skin. Heat rash may manifest as blisters or a red, lumpy rash. Heat rash may feel prickly or itchy, and typically resolves once your skin becomes cooler and sweating decreases.
Contact dermatitis occurs when your skin comes into contact with an irritant or allergen. Laundry detergent is a common irritant for individuals suffering contact dermatitis. Common symptoms of contact dermatitis include an itchy rash — if your underwear is laundered in detergent which is an irritant or allergen for you, it is possible for a rash to develop on your buttocks during running. If you believe your rash is related to irritants or allergens in your laundry detergent, try switching to hypoallergenic detergent, or one intended for sensitive skin.
Allergy to Sweat
It is possible to develop an allergy to your own sweat; this is one possible cause of a buttocks rash while running. You sweat more during strenuous exercise than when at rest, and the increased presence of sweat during your runs could affect the skin on your buttocks. People with the skin condition cholinergic urticaria — one of a number of conditions categorized as "hives" — are typically allergic to their own sweat.