You should consult with your physician. There are several types of over-the-counter allergy medications. Antihistamines can cause sedation and performance impairment. Zyrtec (cetirizine), Claritin (loratadine), and Allegra (fexofenadine) may also cause sedation, but if taken at night, this side effect can be minimized. These three antihistamines are safe to take on a daily basis. Over-the-counter decongestants such as pseudoephedrine (found in Sudafed) and phenylephrine should be used very carefully, they can cause elevated blood pressure, heart palpitations, difficulty falling asleep, and irritability. They're not recommended for patients who have heart conditions, high blood pressure, or hyperthyroidism.