Decongestant nasal sprays can help reduce nasal congestion when you have a cold. But after a few days, the lining of your nose may become less responsive to the medication. You may need more and more nasal spray to control congestion. If you stop using the medication, your congestion may get worse. This is known as rebound congestion. What's the fix? If you use a decongestant nasal spray, use it for no more than three days in a row.