1. Dextromethorphan (cough control)
This acts on the brain—specifically the cough center—to reduce the urge to cough. It doesn’t treat the cause of the cough, but it helps stop persistent dry coughing.

2. Chlorpheniramine (antihistamine)
When you have a cold or allergy, your body releases histamine, which causes runny nose, sneezing, and watery eyes.
Chlorpheniramine blocks histamine, so those symptoms calm down. It also causes drowsiness, which is why the syrup can make you sleepy.