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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