Description: Nasonex Nasal Spray, is a medication used to treat nasal allergy symptoms (sneezing; itchy, runny nose; and congestion). It works by reducing nasal swelling caused by an allergic reaction. NASONEX contains a steroid related to cortisol, a hormone produced naturally by the body. Therefore, because it is administered in the nose, it is considered a "nasal steroid." Talk to your healthcare professional to find out whether NASONEX is right for you or your child.