Over-the-counter decongestant nasal sprays provide fast relief by shrinking the swollen blood vessels in your nasal passages, helping you breathe more easily. Most contain one of two main active ingredients: oxymetazoline (found in Afrin, Dristan, Vicks Sinex and similar generics), which can relieve congestion for up to 12 hours, and phenylephrine (found in Neo-
Synephrine and its generics), which lasts up to four hours.

While bringing almost immediate relief (and an occasional but brief burning sensation in your nasal passage), decongestant sprays or drops cause fewer side effects than oral decongestants such as pseudoephedrine (Sudafed and its generics), in part because they’re mainly topical treatments. That means that unlike pills, they’re usually not absorbed into the bloodstream in significant amounts. (This assumes that you don’t exceed the recommended dose and that you avoid tilting your head back while using the medication, which could cause some of it to drip down your throat.)

Another caveat: Using the sprays for too long can actually leave you feeling stuffier than you were to begin with.

Here are some do’s and don’ts for using nasal sprays, including when to shelve them and switch to an oral decongestant:

1 Do use them sparingly. Three days in a row is the maximum time recommended for taking over-the-counter decongestant drops or sprays. Using them longer than that can lead to rebound congestion — short-term, severe congestion that occurs as the medication’s effect wears off. “When you stop using the spray, the vessels in your nose that have been held in check begin to swell, making you feel congested,” says Beverly Schaefer, an independent pharmacist in Seattle. The rebound effect can last from one to three days, she adds.

2 Don’t double your decongestants. Consumer Reports’ consultants caution against using a nasal spray and an oral decongestant at the same time, for two reasons. First, it’s not necessary, since they work on the nasal passages the same way. Second, taking them together could lead to an overload of decongestant, increasing the risk of side effects. But you might consider switching to an oral decongestant, namely pseudoephedrine, if you still have symptoms after using a spray for three days.

3 Do check with your doctor or pharmacist first. Conditions such as high blood pressure, heart disease, thyroid disease and an enlarged prostate can be made worse by decongestants, including sprays. Call your doctor right away if you experience dizziness, insomnia, tremors, weakness or an irregular or rapid heartbeat while taking a decongestant.

4 Don’t rule out nondrug treatments. Studies have found that using a saline rinse for the nasal passages (called nasal irrigation; saline nasal sprays are also available) can help relieve congestion. And chicken soup really can help you feel better. At least one study showed that it prevented a buildup of white blood cells, which can trigger the inflammatory response that makes you feel so poorly when you have a cold.

5 Do consider what’s causing persistent congestion. OTC nasal sprays are intended to relieve short-term congestion from such infections as the common cold, not to treat prolonged congestion. If your stuffiness lingers, ask your doctor what might be causing it, rather than overdoing it with sprays and risking the rebound effect. You could have an underlying problem such as allergies or a sinus infection. In those cases, the doctor might recommend a medication that’s more appropriate for chronic congestion, such as an antihistamine or a prescription nasal spray that contains a steroid.

Where’s the pseudoephedrine?

Even though pseudoephedrine is available without a prescription, it has been kept behind the counter at pharmacies since 2006 to discourage people from buying it to make the illegal drug methamphetamine. So you’ll have to ask the pharmacist for it.

Note that exceeding the recommended dose can cause dizziness, nervousness or sleeplessness. And even at normal doses it might be unsafe for people with hypertension, heart or thyroid disease, or an enlarged prostate.

In general, it’s best to try a nasal spray first for congestion and switch to pills only if you still have symptoms after three days.

Copyright 2012. Consumers Union of United States Inc.