The siren songs of the spring makeup collections are hard to resist. But think twice before sticking your finger into the lip gloss or eye shadow at the cosmetics counter. There could be more lurking there than the latest shade of plum.

Bacteria, including staph and E. coli, were uncovered in a two-year study of makeup-counter samples conducted by Dr. Elizabeth Brooks, a biological sciences professor at Rowan University in Glassboro, N.J.

“Every single time, we found E. coli. That was the one that was most repulsive to all of us,” said Dr. Brooks, pointing out that this likely means the makeup was tried by someone who didn’t wash her hands after using the restroom.

The study, completed last spring, was a class project for Dr. Brooks’s students, who sampled and cultured cosmetic testers in 20 department stores and pharmacies. Bacterial contamination was found in every sampling, and at a higher rate on weekends, when the stores are busier.

“There isn’t a whole lot of health risk here. The only one I can really think of, and it’s a real possibility, is bacterial conjunctivitis. Also, any of these bacteria can cause acne,” Dr. Brooks said. “It’s just kind of the ick factor. I don’t want this on my skin.”

Dr. Stuart Bender, chief of dermatology at Norwalk Hospital in Norwalk, Conn., and assistant clinical professor at Yale University School of Medicine, agreed that the risk of contracting an infection from contaminated makeup testers is low. “The most dangerous thing at the cosmetics counter is the sticker shock of what it costs,” he said.

Dr. Bender said he typically sees patients with irritations or allergic reactions to cosmetics, but can count on the fingers of one hand the number of times he’s treated a patient for an infection caused by makeup in his 40 years of practicing.

How can you safely try cosmetics? Use common sense.

Wash your hands with soap and water before and after using a makeup tester, or use a hand sanitizer. Try products on your hand, not your face, then hold your hand up to your face to see how the color looks.

“Avoid the eyes and mouth at all costs,” Dr. Brooks said.

Dr. Bender recommends making sure makeup artists put on a fresh pair of disposable gloves each time they help a customer, and use a cotton-tipped disposable applicator when applying products.

Indeed, Dr. Robin Evans, a dermatologist in Stamford, Conn., insists that makeup-counter staff take steps to clean the makeup and spray brushes or use a Q-tip to apply products when testing cosmetics.

“The lips and eyes are much more of an issue than the cheeks,” Dr. Evans said. “Obviously, the risk is there.”

At companies such as MAC, hygiene is a priority.

“We’re very, very serious about it,” Matthew Waitesmith, vice president of artist training and development at MAC, said.

MAC makeup artists undergo mandatory training, learning procedures such as sanitizing lipsticks by dipping them in alcohol and wiping them off; wiping the top layer off powdered cosmetics; sharpening eye pencils between uses, and encouraging customers to test the products on their hands instead of their faces.

The applicators in lip glosses, mascaras, or other products in tubes are removed; clients who want to test them use disposable applicators that have been designed to mimic the package’s design.

“We never double-dip,” Mr. Waitesmith said. “We go through millions and millions of these applicators in a year.” Brushes are washed after each use and deep-cleaned nightly. In addition, makeup artists must wash their hands before doing a customer makeover and use disposable applicators to apply the various products.

Dr. Brooks was not allowed to say which companies’ products she tested, but she acknowledged that the study’s findings had quite an influence on her and her students.

“There is one student – who is going on to medical school in fall – who loves makeup, who said, ‘I will never put anything on my face again.'”