Asthma sufferers who find themselves wheezing and coughing might look to their toothpaste as a possible cause of their problems, two doctors said Wednesday.

An artificial mint flavoring found in a brand of toothpaste made from an opaque paste instead of a gel apparently triggered breathing problems in a 21-year-old woman with a history of asthma.Even though the woman's chest X-rays were normal and she took various drugs for six weeks, the woman had persistent asthma symptoms, including a dry cough, according to a letter published in The New England Journal of Medicine.

Then, she switched toothpastes. She had been using Crest Tartar Control toothpaste, "but when she switched to a gel-based toothpaste her wheezing resolved dramatically," wrote Drs. Bruce Spurlock and Thomas Dailey of Kaiser Permanente Medical Center in Santa Clara, Calif.

When the woman subsequently used any paste-based toothpaste, she started wheezing again within 10 minutes, they said.

After the Procter and Gamble Co. of Cincinatti, which makes Crest, provided Spurlock and Dailey with a list of ingredients in the paste and gel toothpastes, the doctors found the only "absolute difference" between the products was the type of artificial flavoring used.

The gel included a "spice-blend flavoring" while the paste had spice-mint or wintergreen flavoring, the doctors found.

The doctors also discovered that the woman began wheezing when she chewed gum containing wintergreen or peppermint flavoring.

Terry Glover, a spokeswoman for Procter and Gamble, said she was unaware of any other cases in which toothpaste apparently induced asthma symptoms.

But Spurlock and Dailey said doctors who treat patients with such symptoms, especially if they do not respond to drugs, should consider toothpaste exposure as a possible cause.