DEAR DR. DONOHUE: For the past three years I have had to use aspirin or Tylenol several times a day for headaches. My doctor can’t find what’s causing them and doesn’t have any suggestions. Where should I turn? – N.D.

ANSWER: A number of common headache types can become chronic, recurring headaches, and the key to stopping them requires an identification of the headache type.

Migraine headaches can become daily affairs. Migraines are one-sided headaches that sometimes pound with each heartbeat. Physical activity worsens them. People with a migraine want to crawl into a quiet, dark place and be left alone. They’re often nauseated with the headache. Specific migraine medicines are needed.

Chronic tension headaches are another possibility. These headaches are felt on both sides of the head, and people describe them as pressure on or a tightening of the head. Mild activity, like walking, doesn’t make them worse, as it does migraines. Simple pain-relievers can often stop tension headaches.

Post-traumatic headaches are constant headaches that appear after a head injury. I’m sure you would be aware of it if you had had such an injury.

One common thread, however, unites many chronic headaches, and that is overuse of headache medicines. Even though I can’t tell you what variety of headache you have, I can tell you that you are using too much medicine. Overuse increases the frequency and the severity of the headache. To reduce dependence of pain-relievers, you might have to take other medicines while you’re tapering off the pain-relievers. Valproate and topiramate are two examples. Magnesium and riboflavin (vitamin B-2) might also help.

Always eat three meals a day. Skipping meals often brings on a headache. Stay away from ripened cheeses, chocolate, foods that are fermented, pickled or marinated, nuts, peanut butter, sourdough bread, pizza, pepperoni, salami and hot dogs to see if there might be a food link.

You should turn to a neurologist with a special interest in headache treatment.

DEAR DR. DONOHUE: I came back from a two-week camping trip with my two sons. I had crampy diarrhea. The doctor said it was beaver fever. Was he kidding? The medicine he gave me worked. What is this? – W.M.

ANSWER: The medical name for beaver fever is giardiasis (GEE-are-DIE-uh-siss). The giardia germ is a one-celled organism like the ameba studied in high-school biology.

Giardia live in many places, but they are found in fairly large numbers in many surface waters that are easily contaminated by humans or animals. Beavers take a bum rap for it. They are not the only animals that carry and spread it.

Infection sometimes produces no symptoms. Or it can cause diarrhea that requires treatment, and the treatment is usually the antibiotic metronidazole.

How careful were you with the water you drank? Did you boil all drinking water? Or did you treat it with chlorine? Do so on you next trip.

DEAR DR. DONOHUE: I have two painful corns. How can I treat this on my own? I don’t have any medical insurance. – J.S.

ANSWER: Soak your feet in warm water for 15 minutes. Then gently file the corns with a pumice stone, obtainable in all drugstores. File only until you arrive at normal skin. It usually takes more than one attempt before you reach that level.

Your toes are rubbing against your shoes or against each other. Corns are protection against friction. You have to remove the friction to stay corn-free.

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.