DEAR DR. DONOHUE: Our grandson, 6 feet 2 inches, 190 pounds, is in excellent condition and is very active. His only problem is excessive sweating of his feet. After about 3 miles of hiking, he can literally wring the sweat from his socks. Is there something he can do to stop the sweating? — L.D.

ANSWER: Your grandson is far from being the only person in the world with sweaty feet. Each foot has more than 250,000 sweat glands. Why we don’t all have sweaty feet is a bigger mystery than why only a few have them.

Tell your grandson to wear socks made with synthetic fibers like acrylic or nylon. These fabrics wick sweat away from the feet better than does cotton. He needs to carry a couple of changes of socks with him on his hiking trips.

Powdering the feet at least twice a day will help keep them dry.

Before applying powder, spraying the soles with an antiperspirant is another way to solve the excessive sweating. Antiperspirants, although found in the same section of the store as deodorants, are not deodorants. Antiperspirants contain aluminum chloride, and he has to look for this ingredient on the list of components on the can.

If store-bought antiperspirants fail, then a preparation with a higher concentration of aluminum chloride has to be considered. It’s called Drysol, and has 20 percent aluminum chloride. It’s applied every night and washed off six to eight hours later. It requires a prescription.

Another route to take is a battery-powered device that delivers a small electric current to the feet to shut down sweat glands. One such device is Drionic, manufactured by the General Medical Company of Pasadena, Calif. You can contact the company at www.drionic.com or at its toll-free number, 1-855-DRIONIC.

DEAR DR. DONOHUE: Concerning your article Flu Basics, I came down with the flu after getting a flu shot. My understanding is that there are different strains of the flu, and the shot protects only against the strains it contains. So your chances of getting the flu are pretty good. Am I correct in this? — W.M.

ANSWER: You’re correct in saying that a number of different flu strains exist. However, experts, examining outbreaks of flu in countries well before the next season, make a decision on which strains to include in the vaccine for the upcoming year. Their estimates are highly reliable. The flu vaccine affords protection against about 90 percent of strains.

You’re incorrect in saying that the shot gave you the flu. The injectable flu vaccines contain dead virus. Dead virus doesn’t cause an infection. It does prompt the production of protective antibodies. It takes around two weeks for sufficient amount of antibodies in the blood to develop. You can catch flu from an infected person during this period before the vaccine’s effects have kicked in.

DEAR DR. DONOHUE: I am a healthy, 82-year-old woman. Last year, my orthopedic doctor ordered an MRI scan of my right foot. It showed posterior tibial tendinopathy with partial tears. He explained that an operation to correct this problem is quite involved and that I would be healing for a long time. I opted for Plan B: braces and specially fitted orthotics. Two doctors told me this just happens. Is that true? — H.H.

ANSWER: Many times, tendon damage and tendon tears cannot be directly related to a specific cause. In athletes, overuse of the tendons is a common cause. Aging brings about tendon changes that lessen the tendon’s strength and increase its stiffness, two conditions that favor tearing. A few oral antibiotics are also responsible. Cipro and Levaquin are examples. Cortisone shots can also weaken a tendon.

Dr. Donohue regrets that he is unable to answer individual letters, but he will incorporate them in his column whenever possible. Readers may write him or request an order form of available health newsletters at P.O. Box 536475, Orlando, FL 32853-6475. Readers may also order health newsletters from www.rbmamall.com.

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