Dear Dr. Roach: I’m almost 84, and all my life I have had a problem with sinusitis. Never headaches, just post-nasal drip and use of multiple tissues. (I really should buy shares in tissue companies, as I’d rather leave home without my clothes on than without a couple of tissues.) I blow my nose an awful lot.

Anyway, I have always thought that yellow mucus was a sign of infection, but recently my doctor assured me that the color is no longer considered an issue, unless it is a very dark brown. Do you agree with that opinion? — V.M.

Answer: Normal nasal secretions are nearly colorless, and they become colored due to the action of bacteria. So, in cases of bacterial sinus infection, the mucus is usually colored. However, bacteria that normally live in the nasal passages can turn the mucus to a yellow or light-brown color even in the absence of infection. The color intensity is due more to the amount of time the bacteria spend in contact with the mucus. Mucus color is not a reliable indicator of infection.

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 request an order form of available health newsletters at 628 Virginia Dr., Orlando, Fla. 32803. Health newsletters may be ordered from www.rbmamall.com.