Key points
- While the class of anti-allergy drugs called antihistamines are known for their ability to make you drowsy, weight gain can be another side effect of some of these drugs.
- While short-term antihistamine use likely won\’t contribute to weight gain, studies show that some antihistamines have the potential to contribute to weight gain over time.
- Not all antihistamines cause weight gain.
Antihistamines such as Benadryl are a class of drugs commonly used to treat allergies ranging from allergic rhinitis to allergic dermatitis. While they\’re known to cause side effects like drowsiness, a lesser known side effect is their potential to contribute to weight gain.
The reason is due to their effect on the brain.
According to James Walker, MD, board-certified internist and healthcare specialist at Welzo Online Pharmacy, some antihistamines can interfere with the function of a region of the brain called the hypothalamus, which plays a key role in regulating energy expenditure and appetite. As a result, you may feel more fatigued or hungry when taking these medications, as well as less likely to engage in physical activity.
The type of antihistamine you choose and how often you take it may affect whether or not you gain weight. Here\’s what you need to know.
Which antihistamines can lead to weight gain?
While there are no dedicated studies definitively comparing weight gain from different antihistamines, new generations of H1 antihistamines are generally recommended over first-generation medicines due to a better safety profile and their lack of sedative effects. . Experts say they\’re also less likely to contribute to weight gain.
H1 antihistamines work by blocking H1 receptors throughout the central nervous system, preventing histamine from binding to those receptors and causing allergic reactions.
Anne Ellis, MD, a professor of medicine at Queens University in Canada, explains that first-generation H1 antihistamines, such as Benadryl (diphenhydramine) and Chlor-Trimeton (chlorpheniramine), have serotonin receptor activity that can lead to increased appetite and possible weight gain.
This type of activity is largely not seen in second generation antihistamines, such as Claritin (loratadine), Zyrtec (cetirizine), and Clarinex (desloratadine) although some research has found that the use of these drugs was associated with weight gain in the long run use of the term.
How to prevent weight gain from antihistamines
Experts aren\’t sure how much weight gain antihistamines might cause, and there isn\’t enough research yet to make an estimate. But they point out that short-term use of antihistamines is generally not problematic. If long-term use is needed, you should talk to a healthcare professional about the potential side effects and risks.
You can also work with a registered dietitian to establish a balanced diet and healthy lifestyle along with the use of antihistamines. As a general rule, Melissa Baker, RDN, a New York-based registered dietitian nutritionist and founder of FoodQueries, told Verywell that the ideal diet should be high in fruits, vegetables, lean proteins and whole grains, while low in transformed. Mindful eating can be important while taking antihistamines, she added, in order to be more aware of hunger and fullness cues.
Since insufficient sleep of six hours a night is linked to increased appetite and food intake, prioritizing rest can also help offset the side effects of antihistamines.
What does it mean to you
While there have been studies linking weight gain to antihistamines, more research is needed to better understand the interactions taking place. For the most part, short-term use of antihistamines, especially second-generation antihistamines, is unlikely to cause significant weight changes.
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