The earpieces of MP3 players are a breeding ground for bacteria and could lead to painful ear infections, reports The Daily Express.
A study published in the Online Journal of Health and Allied Sciences has revealed that frequent use of earphones significantly increases bacterial growth in the ear.
The Express says researchers at Manipal University in India also found that bacteria could transfer from one person's ear to another's.
Harmful bacteria was found on 92% of ear swabs taken from people who regularly shared their earphones with friends, compared with only 8% of those who shared less frequently.
Dr Chiranjay Mukhopadhyay, who led the research, said, "It is better not to share or else to clean the earphones thoroughly before sharing."