Some over-the-counter medications can make the summer heat more dangerous. Antihistamines, found in cold and allergy medicines, can make the body sweat less, potentially accelerating heat-related illnesses.

“These medications cause the mucus membranes in the body to dry up and actually cause you to sweat less,” says Dr. Greene Shepherd, clinical toxicologist at UT Southwestern Medical Center at Dallas and director of the North Texas Poison Center. “Since sweat is one of the body’s first defenses against heat, this could be serious.”

Diuretics and some diet pills can also be potential sources of problems. These drugs make you shed water faster than normal, either by increased urination or sweating. On hot days, this makes the body more prone to dehydration.

Shepherd recommends people taking these medications be extra cautious during the summer by avoiding strenuous exercise in the heat of the day, drinking plenty of water and watching for the danger signs of heat-related injuries.

Source: UT Southwestern Medical Center