Which of the following increases the risk of heat illness according to the medications discussed?

The correct choice highlights that decongestants and antihistamines can increase the risk of heat illness due to their effects on the body's ability to regulate temperature and maintain hydration. Specifically, these medications can lead to dehydration as they often have drying effects on mucous membranes, reducing the body's capacity to sweat effectively. Sweating is a critical mechanism for thermoregulation, especially in hot conditions.

In addition, antihistamines can cause sedation and may impair cognitive functioning or judgment, which could further compromise an individual's response to rising body temperatures during physical activity. Both medications, therefore, can limit the body's natural cooling mechanisms, enhancing the risk factors associated with heat-related issues such as heat exhaustion or heat stroke.

Other medication categories, while also important, do not have the same direct impact on thermoregulation and hydration that decongestants and antihistamines do. Recognizing the specific effects of these medications helps in understanding how to mitigate risks associated with heat illness in athletic settings.