Does hydroxyzine cause weight gain? No, hydroxyzine isn't known to cause weight gain. This side effect wasn't reported by people taking the drug in clinical studies.

Why do antihistamines cause weight gain?

Why do anti-histamines cause weight gain? Histamine decreases our hunger by in part affecting the appetite control center in our brains[2], and it makes sense an anti-histamine would have the opposite effect. These drugs can interfere with the “I'm full” signal coming from the rest of our bodies and lead to overeating.

What does hydroxyzine do to your body?

Hydroxyzine is in a class of medications called antihistamines. It works by blocking the action of histamine a substance in the body that causes allergic symptoms. It also works by decreasing activity in the brain.