It works by blocking the action of histamine, a natural substance produced by the body in response to allergens. By blocking histamine, fexofenadine helps to reduce allergy symptoms. It can be taken with or without food. However, the dosage may vary depending on the severity of the symptoms and the individual's response to the medication.It's important to note that this medicine may cause drowsiness, so it's recommended to avoid activities that require alertness, such as driving or operating heavy machinery, until you know how the medication affects you. It's also important to talk to your doctor before taking fexofenadine if you have kidney disease, as the dose may need to be adjusted.