If you are physically very active, especially in hot weather, repeatedly sipping cold water is helpful. But beyond two quarts, you may need to also replace the salts lost in sweat — for example, by drinking a diluted sports drink or eating foods with salt and potassium.

Use cotton swabs to clean your ears

Bellybuttons, perhaps, but not ears. My son wishes he had known this earlier, before his two-year-old son copied his dad and punctured his eardrum with a Q-tip. The hole was so big it needed surgical repair.

Dr Snyderman points out that a cotton swab can push wax farther into the ear, causing impaction and diminished hearing. I have long supported the medical adage: Put nothing smaller than an elbow in your ear. If accumulated wax is a problem, try earwax softening drops or have your ears professionally cleaned now and then.

Don’t swim after eating

My parents repeatedly warned us to wait an hour after a meal. It might have been good advice if I were planning to race, swim a long distance or battle a stiff current. Strenuous exercise on a full stomach is never a good idea, because it can result in stomach or muscle cramps. But experts find no harm in a gentle plunge or casual play in the water (pool or ocean) soon after eating.

What can be hazardous is swimming after drinking alcohol, because it can impair judgment and encourage undue risk-taking.

Shaving makes hair grow back faster and coarser

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