Antihistamines and Weight Gain In addition to sedation and dry mouth, antihistamines may have the unwanted side effect of increasing appetite and weight gain.
This may be due to the similar chemical structure of antihistamines and certain psychiatric medications, such as anti-depressants, which are known to increase appetite and lead to weight gain.
Benadryl, and many other older antihistamines, such as Chlor-Trimeton (chlorphenirimine), are available OTC without a prescription.
Learn everything you ever wanted to know about Benadryl.
Older antihistamines, such as Periactin (cyproheptadine), have actually been used for the purpose of increasing appetite and weight gain in underweight children and cancer patients undergoing chemotherapy.
Learn about the use of antihistamines in children and during pregnancy.
In fact, in many states a person can be charged with driving-under-the-influence (DUI) if they operate a motor vehicle while taking medications such as Benadryl.