What Are The Side Effects Of Antihistamines?

Weight Gain

Many types of antihistamines are associated with weight gain. This side effect is so well recognized that some types of antihistamines, including cyproheptadine, are even prescribed to patients who need to gain weight. A 2010 study conducted by Joseph Ratliff found that patients who regularly use prescription antihistamines tend to weigh 4.4 to 9.5 pounds more than individuals in a control group. The same study revealed antihistamine use increased the likelihood a patient would be overweight or obese. Fexofenadine, levocetirizine, and cetirizine are particularly likely to cause weight gain. The drowsiness that could occur with antihistamine use may reduce a patient's physical activity levels, and antihistamines themselves might increase appetite. Patients may wish to monitor their weight while taking antihistamines and make dietary adjustments as needed. If weight gain is concerning, patients may be able to switch to another medication that does not cause this side effect.

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Stomach Pain

Stomach pain is a rare potential side effect of antihistamine use. For some individuals, the pain may be severe. Stomach pain might be related to the urinary retention that can sometimes occur with these medications. In addition, this medicine may lead to constipation, and that could produce stomach pain. Rarely, some patients could experience swelling of the abdomen along with the pain. Patients might want to keep a log of all episodes of stomach pain they experience while on antihistamines. It can be helpful to note any potential food triggers or other issues the patient believes could be contributing to the pain. If stomach pain is severe or continues for more than a few days, patients should see their doctor as soon as possible. It is also important to contact a physician if abdominal pain occurs with burning or pain while urinating. Emergency medical attention is necessary if the abdomen is swollen or if the patient experiences abdominal pain with shortness of breath.