Physicians use the antihistamine hydroxyzine HCL to treat itching induced by allergies, states WebMD. Hydroxyzine HCL's central function is to stop production of histamine during an allergic response. It also addresses mild anxiety conditions and acts as an after-surgery pill to trigger sleep.
Patients use hydroxyzine as directed by the doctor, normally three to four times in a day. A special spoon for measuring the liquid form is also available as using a home-made spoon does not give the correct dose. The doctor determines the dosage based on the patient's age and condition, as reported by WebMD. Constipation, drowsiness, dizziness, dry mouth and blurred vision are possible side effects of hydoxyzine HCL.