Q. I recently went for a routine exam, and the nurse announced he had a really bad sore throat. He did not bother to wash his hands or put on gloves as he took my blood pressure and temperature.

Two days later, I came down with a head cold and severe sore throat, and the following day developed a bad eye infection. I went to an urgent-care center affiliated with my doctor’s office to get my eyes checked out. I told them what had happened, but the doctor said it was impossible for me to catch a cold from the nurse unless I kissed him.

Isn’t it incredibly unprofessional to defend bad behavior? I wonder how many other patients that nurse infected during the course of the day. And I wonder what would have happened if I had asked him to wash his hands.

A. What a shame that the nurse felt he had to work even though he was sick. We agree that it was unprofessional for a physician to defend this lapse in proper hygiene.

Health-care workers are supposed to wash their hands before touching a patient, whether or not they have a cold. Although it should not be up to patients to enforce that behavior, they have a right to request hand-washing by the nurse or doctor.

Q. After trying lots of medications my personal physician prescribed for adult acne, I read a comment in The People’s Pharmacy column about using Listerine on the face. I tried it cautiously, being skeptical at first. Within a short time of starting to use it daily, my face cleared up for the first time in years! I used the original amber Listerine with a cotton ball, dabbing gently on the areas needed. Thank you.

A. We love hearing about home remedies that work. Quite a few people have found that old-fashioned Listerine can help clear up acne, though we do not know quite why.

Q. I have read that you can’t trust the label on some supplements. I guess the Food and Drug Administration doesn’t bother to check them.

If it says “USP” on the container, can we assume that the product is what it says it is?

A. We were appalled to read the research published in JAMA Internal Medicine (online, Feb. 11, 2013) showing wide variations in compounded and OTC vitamin D pills. The scientists found that potency ranged from 9 percent to 146 percent of the dose listed on the label.

You are right that the FDA does not have the resources to check the quality of most supplements. You mention USP, the United States Pharmacopeia. This nongovernmental scientific organization has set quality standards for medicines for nearly 200 years. We spoke with a representative who told us that the USP Verified seal is backed by careful quality monitoring, including off-the-shelf vitamin testing.

Joe and Teresa Graedon answer letters from readers. Write to them via their Web site.