What are some adverse reactions of atarax (hydroxyzine)?

Sleepy. Usually Atarax (hydroxyzine) is safe to use. Only problem is you would feel sleepy/drowsy.
Drowsiness. Atarax (hydroxyzine) is an older antihistamine that works well for itching but commonly produces drowsiness, delayed reaction time and can also cause dry mouth. One should not "drive or operate heavy machinery" while taking atarax (hydroxyzine).