Hey as Hydroxyzine is used to treat itching caused by allergies. It is an antihistamine and here I am giving you its details

Hydroxyzine HCL Uses
Hydrochloric acid is also used in the production of batteries, photoflash bulbs and fireworks. It's even used to process sugar and make gelatin.
Hydrochloric acid, like last month's chlorine compound, sodium chloride, is another "workhorse" chemical because it is incredibly useful in a wide variety of ways.

Side effects
Drowsiness, dizziness, blurred vision, constipation, or dry mouth may occur.
If any of these effects persist or worsen, tell your doctor or pharmacist promptly.
To relieve dry mouth, suck (sugarless) hard candy or ice chips, chew (sugarless) gum, drink water, or use a saliva substitute.

Overdose
If overdose is suspected, contact a poison control center or emergency room right away.
US residents can call their local poison control center at 1-800-222-1222.
Canada residents can call a provincial poison control center.
Symptoms of overdose may include: severe drowsiness, seizures.
In children, mental/mood changes (such as restlessness, irritability) may occur before drowsiness.

Missed Dose
If you miss a dose, take it as soon as you remember.
If it is near the time of the next dose, skip the missed dose and resume your usual dosing schedule