Check which one... It is important to check which form of Hydroxyzine you are using as well. Hydroxyzine pam (pamoate) will help with anxiety. Hydroxyzine hcl (hydrochloride) won't help much. I have even seen pharmacists mix these up and dispense the wrong one on multiple occasions. If you would like a safer and easier over-the-counter medication, try liquid benadryl (diphenhydramine). It's chemically very similar to Hydroxyzine pam.
In proper dosage. It is safe to give Hydroxyzine to a 5 year old before dental procedures. Hydroxyzine is an anti anxiety medication that helps to calm a patient before surgery or similar procedure. It is used to also to control tension and agitation caused by emotional stress but should not be used with a variety of other medications. Hence it should be given only as prescribed by a doctor.