When temperatures climb to 105º in Arizona, most people know the importance of drinking water, finding shade, and limiting time outside. But ABC15's Kaley O'Kelley learned about some common allergy medications that can change the way the body responds to extreme heat and sunlight. Guidance from the Centers for Disease Control and Prevention shows that some antihistamines can reduce the body’s ability to sweat, including diphenhydramine, the active ingredient in Benadryl.