Antihistamines are medications that can treat the symptoms of hay fever and other allergies, according to the MayoClinic.com website. Their mechanism of action involves blocking the action of histamine, which is a substance produced by the body's immune system in response to an attack by a foreign pathogen. Some antihistamines are available by prescription only.
Hydroxyzine (Hyzine)
Hydroxyzine is an injectable antihistamine that doctors prescribe for the treatment of anxiety, and for itching caused by certain allergic conditions. It also works as a sedative in patients before and after they receive a general anesthesia, notes the Drugs.com website. Patients receive hydroxyzine as an injection given by their doctors in an office, hospital or clinic. Drowsiness is a side effect of hydroxyzine, and this effect will be more intense if the patient consumes alcohol while taking this drug. Patients should not drive or do anything that requires alertness until they determine how hydroxyzine affects them. Dry mouth is another common side effect of this medication.
Cyproheptadine (Periactin)
According to MedlinePlus, cyproheptadine is an oral, prescription antihistamine that can alleviate the watery eyes, sneezing and runny nose caused by hay fever and allegies. It can also treat allergic skin conditions, hives and allergic reactions in patients who have received blood products as part of their medical procedures. Doctors may also prescribe cyproheptadine as therapy for migraine headaches. Patients take this drug two or three times a day, and they should take it at the same times every day. Serious side effects may include difficulty urinating, vision problems and nervousness. Patients who experience these problems should contact their doctors immediately. Other side effects include dry mouth, drowsiness, dizziness and nausea.
Fexofenadine (Allegra)
Fexofenadine is a prescription antihistamine that is available for oral use as a tablet, disintegrating tablet, capsule and suspension. It can treat the symptoms of hay fever and hives of the skin, states the MayoClinic.com website. Adults and children 12 years of age and older take fexofenadine tablets or capsules once or twice a day with water. Patients should be aware that taking fexofenadine with apple juice, grapefruit juice or orange juice may lead to an increased risk for certain side effects. In the case of patients who for some reason must drink these juices while taking fexofenadine, it is advisable that they talk with their doctors to determine if a dosage adjustment is necessary. Side effects may include tightness in the chest, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, feet, legs or sex organs, shortness of breath, vomiting, body aches, chills, diarrhea, dizziness, sore throat and swollen joints.
