Nimesulide is a non-steroidal anti-inflammatory drug (NSAID). It works by blocking the release of certain chemical messengers that cause pain and inflammation (redness and swelling). Phenylephrine is a decongestant which narrows the small blood vessels providing relief from congestion or stuffiness in the nose. Cetirizine is an antiallergic which relieves allergy symptoms like runny nose, watery eyes and sneezing. Caffeine is a stimulant which decreases sleepiness caused by Cetirizine.