While pollen generally is to blame for triggering allergy symptoms in the springtime, grasses and weeds usually are to blame for summer allergies. Summertime allergies bring on a host of symptoms including itchy and watery eyes, runny nose, sneezing, and coughing. But some of the medications to relieve those symptoms can have an adverse effect on your body. That's why it's important to carefully heed your doctor's instructions to avoid heat-related illness brought on by a side effect of allergy medication.

Role of Antihistamines in Relieving Allergy Symptoms

Your body makes histamine during an allergy attack, causing your uncomfortable symptoms. Histamine is a chemical the body releases as an immune response to allergens, causing an inflammatory reaction. Antihistamines block the release of histamines, easing symptoms like nasal congestion, a runny nose, and postnasal drip.

But prescription or over-the-counter antihistamines you take to reduce sinus congestion due to allergies can interfere with the function of the autonomic nerves, which stimulate the sweat glands. Therefore, a potential side effect of antihistamines is that your body produces less sweat. That can lead to additional health-related problems, especially if you're older.

Role of the Autonomic Nervous System in Cooling the Body

The autonomic nervous system is a complex network that includes the thermoregulatory system, which aids the body in maintaining a steady body temperature. Heat loss from the body occurs through evaporation of body water in the form of sweat.

Normally, when your body's internal temperature rises too high and you get overheated, you start to sweat as a way to lower the temperature. But when something interferes with the sweating mechanism in your body, it's not going to respond the way it should and you may not sweat.

Health Risks When Your Body Temperature Rises Too High

Since sweat keeps the body cool, you are at risk of heat stroke if your body can't regulate its temperature and that temperature rises too high. Symptoms of heat stroke include nausea, dizziness, headache, rapid pulse, and skin that becomes red, hot, and dry from not sweating. Because heat stroke can be a medical emergency, if you suffer from allergies, your doctor may recommend drinking plenty of fluids—preferably water—moving slowly, avoiding intense physical activity, and remaining in the shade and out of the heat when outdoors.

If you experience anhidrosis—lack of sweating—as a result of the use of antihistamines to relieve allergy symptoms, another option is the use of decongestants to reduce the amount of fluid in the lining of your nose. Decongestants help relieve congestion by shrinking swollen nasal passages.

But if your allergy symptoms are severe, your doctor may recommend allergy shots or under-the-tongue tablets, which is another option for immunotherapy to treat hay fever and other allergies triggered by grass pollens.