What is Allegra? Allegra is an antihistamine that reduces the natural chemical histamine in the body. Histamine can produce symptoms of sneezing, itching, watery eyes, and runny nose. Allegra is used to treat the symptoms of seasonal allergies (hay fever) in adults and children. Allegra is also used to treat skin itching and hives caused by a condition called chronic idiopathic urticaria in adults and children. Important information about Allegra Before using Allegra, tell your doctor if you are allergic to any drugs, or if you have kidney disease. Fruit juices and certain antacids can make it harder for your body to absorb Allegra. Take the disintegrating tablet on an empty stomach, at least 1 hour before or 2 hours after a meal. There may be other drugs that can affect Allegra. Tell your doctor about all the prescription and over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other doctors. Do not start using a new medication without telling your doctor. Stop using Allegra and get emergency medical help if you think you have used too much medicine, or if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Less serious side effects are more likely, and you may have none at all. Tell your doctor about any unusual or bothersome side effect. Tell your doctor if your symptoms do not improve, or if they get worse after you start taking Allegra. Never take more of the medication than your doctor has prescribed. Before taking Allegra Before using Allegra, tell your doctor if you are allergic to any drugs, or if you have kidney disease. FDA pregnancy category C. This medication may be harmful to an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant during treatment. It is not known whether this medication passes into breast milk or if it could harm a nursing baby. Do not use Allegra without telling your doctor if you are breast-feeding a baby. Allegra tablets and capsules may be used to treat seasonal allergy symptoms in children who are at least 6 years old. Allegra oral suspension (liquid) may be used in children ages 2 through 11. When treating chronic idiopathic urticaria, the liquid may be used in children as young as 2 months old.