it depends on your symptoms. antihistamines generally relieve allergy-type symptoms like itchy and watery eyes runny nose sneezing and itchy throat. decongestants are helpful to relieve sinus congestion and pressure as well as nasal congestion. rule of thumb: you want to take the smallest number of medications to treat most of your symptoms and to minimize the number of potential side effects. so if you have runny nose and watery eyes and no congestion an antihistamine-only product is a good choice. if you ever have questions about which over-the-counter medication to choose ask your pharmacist.
i never know when to take an antihistamine or decongestant so i end up buying a product with both. is that a good idea?