Ear aches (swimmer's ear)
What it is
There are multiple types of ear infections, and different possible causes. Some are due to bacteria, some to chemical imbalances (like in pool water), and some due to fungi. Sometimes, it's even a combination of these.
The one that most often affects swimmers is called otitis externa. It affects the external canal that leads from the outer ear to the eardrum and is frequently called "swimmer's ear."
Water that stays in the ear canal can cause irritation and a breakdown of the lining of the canal, allowing bacteria or fungi to find a nice place to stay, resulting in an infection. This frequently happens to swimmers -- getting water in the ear canal is a natural part of swimming.
The infection causes ear pain, sometimes severe, especially with movement of the ear lobe.
How to avoid it
There are two approaches to preventing ear infections: dry the ear out after swimming, or keep water from entering in the first place.
The best prevention is a half-and-half mixture of rubbing alcohol and white vinegar -- three drops in each ear after a swim. The alcohol helps to dry the canal while the acidic vinegar retards growth of bacteria and fungus. You can buy over-the-counter mixtures that do the same thing, but they cost a lot more.
A different approach is to stop the water from entering in the first place by wearing well-fitted ear plugs. Do not use Q-tips for drying because they can irritate the skin that lines the canal, which actually makes an infection easier to establish.
Sometimes excess wax in the ear canal doesn't allow the water to drain completely, resulting in continuous moisture.
What to do if you've got it
Otitis externa is usually treated with ear drops that contain an antibiotic and may also contain a steroid or cortisone-like medication to reduce inflammation. But because there are so many possible causes, consult a doctor rather than trying to medicate yourself. Fungal infections can be a lot more complex than bacterial ones and are treated differently.
If the doctor prescribes antibiotics, be sure you finish the complete course that was prescribed rather than stop as soon as the irritation starts to subside. That helps prevent relapses and eliminates those pesky little bacteria so they aren't able to rally and develop a resistance to the antibiotic.