Bowlers get blisters on their thumbs. Runners get them on their feet, and tennis players and rowers get them on their hands. When you rub an area of skin repeatedly, the friction causes the top layer to separate from the bottom layer, and fluid separates them. Wetness and heat markedly increase your chances of getting blisters. Wetness causes the skin to stick and increases the shearing force on it. Heat increases the chances of the outer layer of skin separating from its lower layer.
When you start to develop a blister, your skin will hurt. You can usually prevent the blister by stopping the rubbing. Check the cause: If it's on your inner thighs, you may need a pair of shorts that have less material between your thighs. If it's on your tennis hand, you may need a racket with a different grip. If it's on your feet, you may need new shoes or socks.
If you are in an important competition and have to keep going, stop temporarily, if you can. Dry the rubbed area with a towel and cover it with a piece of tape and sprinkle the area with powder. The tape absorbs the friction to reduce heat and the powder absorbs some of the sweat to help keep you dry.
A blister will heal faster if the fluid is removed. A trained person can sterilize the area with alcohol, insert a sterile needle into the skin at the side of the blister and press out the fluid gently without tearing the skin. Then put a piece of tape over the blister to hold the top layer of skin tightly to the bottom layer.
Q: When I run in very cold weather, I worry about frostbite.
How can I tell if I'm getting it, and how do you treat it?
A: It's far easier to prevent frostbite than to treat it. You'll have plenty of warning. When the outside temperature is between 77 and 80 Fahrenheit, your nude body temperature does not change. However, at temperatures below that, your body temperature starts to drop rapidly. Your normal skin temperature is between 90 and 96. When you expose yourself to cold, your body works to retain heat, the blood vessels in your skin close and your skin temperature starts to drop. When it reaches around 59 degrees Fahrenheit, your body tries to save your skin. The blood vessels open up and the skin turns red and hot and starts to itch and burn. When this happens, dry yourself and get out of the cold and your skin will rewarm rapidly. However, if you remain in the cold, your skin temperature starts to drop again.
If the outside temperature is below 26 degrees, your skin can freeze and you can develop frostbite. To prevent frostbite, get out of the cold when your skin turns red and starts to itch and burn. Never rub anything on frostbitten skin. All it does is remove skin. The treatment for frozen skin is for a doctor to rewarm the skin rapidly in water warmed to 100 to 108 degrees Fahrenheit.
Q: A friend tells me my resolution to lose weight can do me more harm than good. Is she just trying to justify her own extra pounds?
A: Starting a diet that you can't stay on can harm you because repeatedly losing and gaining weight shortens your life. Every time you lose weight rapidly, you can form gall stones and your bones lose calcium. Every time you gain weight rapidly, you form plaques in your arteries.
You can't stay on very low-calorie diets, or those that omit protein or carbohydrates. Low-calorie diets are ineffective for permanent weight loss because they leave you hungry all the time. You can stay on a low-fat diet forever because it is based on plant foods with lots of fiber, and fiber makes you feel full even though it supplies no calories.
If you want to lose weight permanently, you have to change your lifestyle so that you exercise more. How fat you are has more to do with how active you are than how much you eat. Try to alternate two sports on successive days and stop exercising immediately when you feel tired or hurt. I recommend alternating a stationary recumbent bicycle. You can read or watch television comfortably while you pedal and sit on a contoured chair. You prevent injuries by allowing 48 hours recovery for your legs when you switch to an upper body exercise such as rowing on the next day. For permanent weight loss, it's exercise and a low-fat, high-fiber diet.
Dr. Mirkin is a practicing physician in Silver Spring specializing in sports medicine and nutrition.