How Dirty Is Your Makeup?

May 13, 2010— -- We've all been there – you see an eye shadow or blush compact in your makeup bag but you're not quite sure how long you've had it. No harm in using it one more time, right? Not so fast.

It turns out that all it takes are a few cells from an unwashed hand or a blistered lip and a mascara wand or lip gloss could become a haven for contagious bacteria.

Hundreds of people use makeup counter testers every day, but unfortunately not everyone uses the disposable applicators provided. Dirty fingers dipped in makeup can spread everything from herpes to pink eye.

"You can find staphylococcus, you can find micrococcus…and if you're very unlucky…E. coli, which is obviously from fecal matter," Dermatologist Jeanine Downie said.

That same bacteria might be hiding in your own makeup stash, especially in older products. Antibacterial agents start to break down after about six months.

Former makeup artist Syama Meagher said she still uses products that are months, years and even decades old, like her favorite high school eye shadow from the early '90s.

"If I put it on my finger or my hand and it looks okay I figure, why can't I use it?" Meagher said.

"GMA" wanted to find out just how unhealthy it is to use makeup past its prime, so we collected a few samples to send to a lab: lip gloss from Meagher, liquid eyeliner from our own Juju Chang and mascara and eyeliner pencil from some "GMA" staffers.

ABC News correspondent Andrea Canning had face powder, which was at least a year old, months-old mascara, concealer and worn down lipstick and sent them off to be tested.

Andrea said "it might not be pretty" and she was right -- the results were shocking. Of the 25 samples tested, 11 came back positive for different types of bacteria such as staphylococcus, commonly found on the skin but still potentially harmful.

"This is a bacterium that can cause pink eye…and also skin lesions and rashes," microbiologist Connie Morbach said.

We discovered streptococcus, which is usually found in saliva or mucous, and Morbach said is a bacterium that can cause strep throat.