A study at Kasturba Medical College in Manipal, southwest India, has found that listening to iPod can raise the chance of getting earache.
The Indian boffins also discovered that sharing in-earphones is hazardous for health, as bacteria can get passed from one user to another.
According to scientists, regular users of iPods and other mp3 players had higher rates of bacterial infection than those who were not regular users, reports the Telegraph.
The study involved 50 health medical students, half who said they were regular users (Group B) of iPods and half who said they were not (Group A).
The researchers found: "Group B showed heavy growth and a significant increase in the number of bacterial growths after frequent and constant use."
Bacteria was found in the ears in 92 per cent of those who did use in-earphones regularly and 80 per cent of people who did not.
They concluded: "Frequent and constant use of earphones increases the bacterial growth in the ear."
Sharing earphones "might be a potential vector" for bacteria, they added.
In the study, researchers discovered bacteria that included types of Staphylococcus - the ones which can cause swelling in the ear and earache.
The microbiologists said: "The majority of the isolates were Staphylococcus spp. (MSCONS) which although a normal skin flora most often, could well be a pathogen if the condition is congenial. Cheaper quality [of earphones] or improper use may give rise to abrasion, leading to breakage of the skin which might be a portal of infection."
The study has been published in the Online Journal of Health and Allied Sciences.