Pimples originate in pores in the skin. Pores contain cells that produce hair and glands that secrete oil called sebum. The body is covered in skin pores that are susceptible to becoming clogged with dirt, oil and bacteria, which causes pimples. The National Institutes of Health indicates that even though acne is most common on the face, it also can occur on legs.
Tight pants and shorts can rub against legs and cause acne. Certain fabrics, such as polyester, prohibit skin breathing and can prevent the skin from getting proper ventilation. Snug socks can also cause acne by holding sweat close to the skin.
Sweating alone won’t create pimples, but combined with oils, dirt and bacteria, sweat can clog pores and cause breakouts. Legs are susceptible to sweating in hot weather. Acne can also appear when the skin on the thighs rubs together, which is common in people who wear shorts, dresses and skirts.
If you break out after exercising at the gym, it’s not necessarily the sweating that’s causing your acne to flare up. The mats used at gyms for stretching and yoga and exercise equipment benches are made from a type of material that can block pores. If you sweat while using gym equipment, your pores can become blocked and clogged with sweat and bacteria. To prevent breakouts, wear long, breathable workout pants.
Moisturizers and sunblock can cause breakouts on the legs, especially if the product is oil-based. Water-based cosmetics, and those that are labeled noncomedogenic (which means they’re formulated to reduce pimples) are less likely to clog pores.
Hormones can trigger sebaceous glands, especially during times of stress, menstruation and pregnancy. Teens are especially prone to breaking out during puberty when their systems are flooded with hormones and their sebaceous glands are first activated. To prevent hormonal breakouts, a daily skin-cleansing regimen can reduce sebum production.