Honeywhite, I'm not knocking you man, but in the future, it might be easier for you to handle more simple questions by simply Googling them and conducting your own research. We're always here to help you and we want you to acquire the knowledge necessary to be an effective contributor. We want you to become an effective researcher in your own right so that you can come back and use your skills to help other BL'ers who are in the position you're in now.
If you were to Google "Hydroxyzine", you'll be confronted with suitable resources like Wikipedia and you'll find out that Hydroxyzine (Vistaril, Atarax) is a sedative antihistamine of a similar nature to other drugs of the class, which include Diphenhydramine (Benadryl), Promethazine (Phenergan) and Doxylamine (Unisom) among others. There's not a significant or extremely noticeable difference between any of these drugs. I would challenge someone to differentiate the two. It's like preferring Coke over Pepsi. There are some people who have their preferences, but in a pinch, each can be substituted for one of the others.
I feel like the medical establishment has almost randomly assigned various positive effects to different antihistamines that aren't really correct. "Hydroxyzine is an anxiolytic"; "Promethazine is an antiemetic"; "Diphenhydramine is for allergies". It seems almost arbitrary. I'm a bit of a conspiracy theorist, but I have a firm belief that the reason why some of these antihistamines are prescription-only medicines is because, by labeling them as "controlled", less-informed patients might be more inclined to believe that these drugs are indeed effective. Prescribers will rarely say "oh yea, this is just an antihistamine by the way", it's more like "we have a very effective anxiolytic known as Vistaril that is indicated for your condition. It's nearly as effective as Benzodiazepines for anxiolysis.
The pharmaceutical companies slap a "new and improved" sticker on a box of antihistamines, claiming antihistamines will conquer your mental illness and make everything alright. So, instead of say, buying 600 Diphenhydramine (Benadryl) tablets from Costco for $5, you can pay $15 for 10 tablets of Hydroxyzine that will really not produce any kind of profoundly different effect than any of the other antihistamines.
Case in point, all of the sedative antihistamines are almost totally interchangeable. The relegation of certain antihistamines to prescription-only status is totally arbitrary and most likely a very sneaky way of psychologically attracting new patients.