Antihistamines are commonly used medications that help alleviate symptoms associated with allergies, such as sneezing, runny nose, and itching. They work by blocking histamine, a natural chemical released by the body during allergic reactions. While effective for allergy relief, a frequent concern among users is the potential for weight gain.
Antihistamines and Weight Changes
Antihistamines can be associated with weight changes, though this is not a universal side effect. Research indicates a correlation, especially with chronic use of certain types. For instance, a 2010 observational study found that adults taking antihistamines had a higher average weight and larger waist circumference compared to non-users, an association also observed in children. Studies do not definitively prove a direct cause-and-effect relationship, and more research is needed. Short-term or intermittent use is generally less likely to result in significant weight changes compared to regular, long-term use.
How Antihistamines May Influence Weight
Antihistamines may influence weight through their interaction with histamine, which plays a role beyond allergic responses. Histamine acts as a neurotransmitter in the brain, where it helps regulate appetite and metabolism. Histamine normally reduces food intake by acting on H1 receptors in the hypothalamus, a brain region involved in appetite control. When antihistamines block these H1 receptors, this natural appetite-suppressing effect can be diminished, potentially leading to increased food intake.
Antihistamines may also affect energy expenditure and metabolism. Some antihistamines can cause drowsiness or fatigue, which might lead to reduced physical activity and, consequently, fewer calories burned. The exact mechanisms are still being investigated, but antihistamines might indirectly promote weight gain by altering metabolic processes. Animal studies have shown that blocking histamine can result in increased eating and weight gain.
Differences Among Antihistamine Types
Antihistamines are broadly categorized into first-generation (sedating) and second-generation (non-sedating) types, and their propensity for weight gain varies. First-generation antihistamines, such as diphenhydramine (Benadryl) and chlorpheniramine, more readily cross the blood-brain barrier. This characteristic makes them more likely to cause drowsiness and interfere with histamine’s role in appetite regulation. Some older antihistamines like cyproheptadine have been used to stimulate appetite and promote weight gain.
Second-generation antihistamines, including loratadine (Claritin), cetirizine (Zyrtec), and fexofenadine (Allegra), are designed to be less sedating because they do not cross the blood-brain barrier as easily. While generally considered to have a lower risk, some studies have linked long-term use of second-generation antihistamines like cetirizine and fexofenadine to weight gain. Loratadine appears to be associated with less weight gain compared to other antihistamines, partly because it is less likely to induce drowsiness or significantly affect the brain’s appetite centers.
Addressing Weight Changes While Using Antihistamines
Individuals concerned about or experiencing weight gain while using antihistamines should consider several practical approaches. Discussing these concerns with a healthcare provider is an important first step. A doctor can evaluate individual circumstances, assess the need for the medication, and discuss potential alternative treatments or adjustments to the current regimen. They may consider switching to a different type of antihistamine, especially a second-generation one that may have a lower association with weight gain.
Alongside medical consultation, adopting healthy lifestyle practices can help manage weight. Maintaining a balanced diet rich in fruits, vegetables, lean proteins, and whole grains, while limiting processed foods and sugars, is important. Regular physical activity can also counteract reduced energy expenditure that some antihistamines might cause. Ensuring adequate sleep and staying hydrated can further support weight management.