This information is for people who have anxiety disorder. It tells you about hydroxyzine, a treatment used for anxiety disorder. It is based on the best and most up-to-date research.
Does it work?
Yes, probably. Studies suggest hydroxyzine works better than a dummy treatment used for comparison (a placebo). Hydroxyzine also seems to work about as well as buspirone and benzodiazepines, two other drug treatments for anxiety disorder. But there isn't enough good research to be certain. We didn't find any good-quality studies to say if it works or not for children and teenagers.
What is it?
Hydroxyzine belongs to a group of drugs called antihistamines. These drugs make you feel calm and may make you feel sleepy. Doctors sometimes give hydroxyzine to people who are nervous before having surgery.  Your doctor may offer you an antihistamine if your anxiety suddenly gets a good deal worse. Antihistamines are normally only prescribed for a few weeks.
You can take hydroxyzine as a tablet or a liquid. Brand names for hydroxyzine are Atarax and Ucerax.
If you take hydroxyzine, you should feel the calming effects within a few hours of the first dose. Higher doses make you sleepier than lower doses.
How can it help?
Studies suggest that hydroxyzine improves people's symptoms.  Researchers measure symptoms using symptom rating scales. They look for improvements in a long list of symptoms including worry, tension, fear, and depression. They also look for overall improvements in how you feel.
Hydroxyzine seems to work about as well as two other treatments for anxiety disorder - buspirone and a benzodiazepine called bromazepam.  But we need more studies to be certain.
How does it work?
Hydroxyzine is an antihistamine, which means it blocks the effects of a chemical called histamine. Blocking the effect of histamine in your brain makes you feel calm.
Hydroxyzine works in a similar way to benzodiazepines. Doctors know that benzodiazepines help people with anxiety disorder, so they think that hydroxyzine might also work as a treatment for anxiety disorder.
Can it be harmful?
Hydroxyzine can cause side effects, including headaches and drowsiness. 
If you take a drug that makes you sleepy, you're more likely to have an accident. If you're feeling drowsy, do not drive or operate any machinery.
How good is the research on hydroxyzine?
The research on hydroxyzine is reasonably good. We found a summary of the research (a systematic review) that included five good-quality studies ( randomised controlled trials). 
The summary found that people who took hydroxyzine were more likely to have their symptoms improve than people taking a dummy treatment (a placebo). The summary also found that hydroxyzine seemed to work as well as two other treatments for anxiety disorder - buspirone and a benzodiazepine called bromazepam. However, we need more research to know for certain.