We recently tested 467 makeup products, donated to our study by people in the United Kingdom, for bacterial and fungal contamination and found that 90 percent contained potentially deadly germs. These products, which included lipstick and mascara, could pose a significant health threat.
We found E. coli and Staphylococci in used eyeliner and mascara. These bacteria can cause irritation and conjunctivitis (pink eye). Although the symptoms of conjunctivitis tend to be mild—itchy, watery eyes—in extreme cases, it can lead to sight loss. The germs causing conjunctivitis also can spread to other parts of the body, which can trigger a more serious secondary infection.