DEAR DR. ROACH: I’m asking this question for my sister. Is it safe to use a nasal rinse solution when one has a sinus infection with green phlegm? She also sufferers from a deviated septum, dysfunctional Eustachian tubes and vestibular disorder with vertigo and tinnitus. — K.C.H.

ANSWER: Sinus infections are common. Most are caused by viruses. Although antibiotics have long been prescribed for these infections, most people do not need them; symptoms will get better without antibiotics. Only people with symptoms lasting longer than 10-14 days or who worsen after initially getting better should consider taking antibiotics. Green-colored mucus does not predict bacterial infection, contrary to popular belief.

Nasal irrigation is a good way to relieve symptoms, and it is safe for most people. It can help loosen the mucus so it can drain more easily, and irrigation relieves inflammation by literally washing away pro-inflammatory substances.

People with a mildly deviated septum should have no trouble using a saline rinse, but a very severe deviation may make the process hard mechanically. The Eustachian tubes, which allow pressure to be equalized between the middle ear and the back of the throat, are not at issue for people using a saline rinse. A vestibular disorder could be triggered, in theory, with very cold water, but I think it would be unlikely to cause your sister problems with warmed (no more than body-temperature) water.

The fluid used for nasal rinse should be made using sterile or bottled water. There have been rare instances of amoeba infections from using tap water. I found some nice directions on how to do the nasal wash at https://www.healthlinkbc.ca/health-topics/hw67090.

DEAR DR. ROACH: My roommate will throw out food that is one day past the expiration date, but has prescription drugs that are over 10 years old in the medicine cabinet. Are old drugs dangerous or just ineffective? — R.D.

ANSWER: I think your roommate is wrong on both counts: Most food is good at least a few days after its listed expiration, and keeping expired medication way past its due date is potentially dangerous.

Expired medication, certainly if it’s a year past its expiration date, often is ineffective. There are exceptions — some medications are very stable if kept dark and cool — but it is not wise to count on that. Further, a few medicines, especially the tetracycline class of antibiotics, actually are dangerous and may cause kidney damage if taken past their expiration date. This is almost unheard of nowadays, fortunately.

DEAR DR. ROACH: I had a severe case of shingles several years ago, after I had had the shingles vaccine that was available at that time. Should I get the new vaccine, even though I’ve already had shingles? There seems to be divided opinions on it. — P.C.

ANSWER: Most authorities still would recommend the new and much more effective Shingrix vaccine to someone in your situation. I’m sure you don’t want another case of shingles, and it is possible to get shingles more than once. However, the risk is still low in absolute terms, so I wouldn’t say this is a very high priority. Given the difficulty finding the vaccine in many parts of the U.S., you could safely wait until it is more available. In my opinion, the harm of an adverse reaction is so small that even the modest benefit in reducing risk is worth it. Cost is an issue for some people.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or send mail to 628 Virginia Dr., Orlando, FL 32803.

Dr. Roach