You don't have to swim very often to get an ear infection. The swimming pool and the sea both contain bacteria and swimming can cause ear infections. The water swilling around in your ear canal softens the skin and lets the bugs in where they cause pain, itching, redness and swelling. Pus causes discharge and debris build up in your ear canal, causing deafness. This is called conductive deafness, as opposed to sensorineural deafness caused by nerve damage. Swimmers' ear is inflammation and infection of the outer ear and ear canal. It can be treated with ear drops containing antibiotics. Some varieties contain anti-inflammatories and antifungals. Now you know the answer to 'Can swimming cause ear infections?'
Otitis externa can spread to the middle ear causing otitis media. This needs treatment with antibiotic drops and oral antibiotics. It is usually more painful than otitis extern as pressure builds up behind the ear drum. Inflammation prevents the Eustachian tube draining the middle ear into the nasal cavity. Fluid accumulates behind the eardrum causing it to bulge which is painful. Eventually the eardrum (tympanic membrane) may burst. Initially this is very painful but subsequently relieving the pain. Blood and pus may discharge from the ear and the tympanic membrane is left with a hole in it. If this is small then hearing may be unaffected but if large then deafness may be present.
The perforated eardrum should heal in 4-6 weeks although it may take longer than this. It is important for a competent medical practitioner to examine the ears. This is to check that the drum heals otherwise an operation may be required to repair the hole.
Prevention is better than cure. A good pair of ear plugs for swimming will stop the water and bacteria entering your ears and causing the infection in the first place. A good pair of swimming ear plugs will be non-porous, antibacterial and connected by a cord so you won't lose them, a pair from ZenPlugs are ideal.