That cocktail party canapé wouldn’t be the same without a bit of aged cheese, finely marbled with a deep-blue mold. But out of the buffet line, mold also stars throughout medical history.

Thousands of years ago, the Chinese placed moldy soybean curd on open skin wounds. Other cultures used warm mold-containing earth to treat injuries. And in the 1920s, Dr. Alexander Fleming discovered penicillin, derived from bacteria-inhibiting mold.

But when it comes to our health, mold sometimes proves more dastardly than divine. News reports have highlighted the danger of so-called “toxic” molds flourishing in homes, schools and other buildings.

Mold spores take up residence after entering through doorways, windows or ventilation systems. They lurk in ductwork, shower stalls or near leaky pipes. Materials such as wood or wallpaper can feed the mold, and the air conditioning system can spew its spores.

Most molds are harmless. Only a small percentage potentially cause health troubles. And although news reports have linked mold toxins to pulmonary hemorrhage, memory loss or cancer, the connection hasn’t been scientifically proven.

Far more common are mold-related allergy symptoms such as hay fever or eye irritation. People with chronic respiratory diseases might have difficulty breathing or develop lung infections.

If you see or smell mold, remove it by cleaning with a bleach solution. For more extensive growth, contact a professional. Repair leaks and replace anything that gets wet to prevent long-term problems. And see your doctor if you suspect a mold-related health problem.