A decongestant is a medicine you take when a cold or hay fever has blocked your nose or sinuses, so you can breathe more easily. It comes as a pill, a syrup, or a spray up the nose. It does not make the cold go away; it only eases the blocked feeling for a while, by shrinking the swollen lining inside the nose. Though actually, not every 'cold medicine' is a decongestant. Some only bring down a fever or quiet a cough. Nose sprays can work fast, but if you use them for too many days in a row, the blocked feeling can come back worse. This is a pharmacy word. At home people often just say they need something for a blocked nose.

減充血劑。藥局這樣標；日常多說鼻塞藥、通鼻噴劑。不是普拿疼——普拿疼是止痛退燒，不負責通鼻。