Rexnol DX Syrup is a combination medicine used to treat dry cough by reducing the activity of the cough center in the brain. It relieves allergic symptoms like runny nose, watery eyes, sneezing, and throat irritation. The dose depends on the patient's condition and response. Common side effects include nausea, upset stomach, and rash, which usually resolve over time. It may cause dizziness and sleepiness, so avoid driving or mental focus until you know how it affects you.