Studies have shown that people with obesity are more prone to allergies, and this may have to do with the medications used to treat seasonal allergies. Scientists from Yale University published a study in 2010 in the journal Obesity showing that people who took antihistamines gained weight. Histamine is known to affect body weight. The appetite control center of the brain known as the hypothalamus contains receptors for histamine. When histamine receptors are blocked by an antihistamine medication, the brain doesn’t receive the “I’m full” signal like it normally would. The body also can’t burn calories effectively when the histamine receptor is blocked, lowering metabolism. These biological changes result in increased appetite, overeating, slower fat breakdown and weight gain. Antihistamines can also make you feel tired and unmotivated to exercise.
Antihistamines that can cause weight gain include:
Diphenhydramine (Benadryl and others)
Cetirizine (Zyrtec)
Levocetirizine (Xyzal)
Fexofenadine (Allegra)
Hydroxyzine (Atarax, Vistaril)
Chlorpheniramine maleate (Chlor-Trimeton)
If you need to take an antihistamine your best bet is loratadine (Claritin). This is because loratadine does not cross into the brain and therefore cannot stimulate the appetite center of the brain and does not cause fatigue.
Alternative allergy treatments include steroid nasal spray and eye drops, decongestants, cromolyn sodium nasal spray and allergy shots. Frequent showers and salt-water nasal washes can also be helpful. Non-drug strategies for dealing with allergies include reducing exposure to allergy triggers like pollen, mold, or pet dander.
