DEAR DR. DONOHUE: I am having a horrendous bout of diarrhea. I have had it for more than five weeks. The doctor did a sigmoidoscopy and a biopsy, but nothing was found. No one knows what to do except to hope it leaves on its own. Help. – L.R.

ANSWER: Diarrhea that lasts for more than four weeks qualifies as “chronic” diarrhea, and that eliminates the more common causes of diarrhea, like viral infections. It doesn’t eliminate all infections, however. If you did any traveling before the diarrhea appeared, you might have a parasite that’s staying with you and refuses to leave.

Diseases that interrupt normal food absorption have to be considered. The pancreas makes many digestive enzymes, without which food passes through the tract rapidly and as diarrhea. Celiac disease is another cause of malabsorption and is another example of an illness that has to be considered. Hyperthyroidism – an overactive thyroid gland – can have diarrhea as one of its signs.

If there is blood in your stool, then things like ulcerative colitis are possible, as is Crohn’s disease. Both are inflammation of the digestive tract.

A deficiency of the lactase enzyme – the enzyme that digests milk and other dairy products – can lead to diarrhea.

A sigmoidoscopy is a good test, but you need more. You need to see if your digestive tract is not absorbing food as it should. You would also benefit from a colonoscopy – an examination of the entire colon. A sigmoidoscopy examines only the terminal portion of it.

While the search for a cause is going on, ask your doctor if you might try Imodium, Lomotil or Pepto-Bismol to slow down the number of stools you’re having.

DEAR DR. DONOHUE: I am 66. I have dealt with a skin problem since I was 19 – tinea versicolor. At one point I was prescribed griseofulvin, which helped, but only temporarily.

I am awoken from sleep because of this miserable affliction. Do you have any suggestions on how to control it, other than wishing for an early death just for relief? – N.P.

ANSWER: Tinea versicolor is a fungal infection of the skin that produces depigmented or hyperpigmented patches that start out about .4 inch in diameter. Adjacent patches can fuse to form larger patches. Depigmented skin is more common than hyperpigmented skin. In the summer, when people are tan, the colorless patches stand out prominently. They can appear on the trunk, the upper arms or legs, and sometimes the face.

Ordinarily, tinea versicolor produces no symptoms. In some, it itches.

Tinea versicolor can usually be treated with a number of antifungal medicines, including Lamisil cream or selenium-sulfide lotion. In very bad cases, oral Nizoral is prescribed.

There are so many elements of your story that are not typical of tinea versicolor that my suggestion is to see a dermatologist for confirmation. Skin scrapings, examined with a microscope, provide evidence of the fungus. Tinea versicolor usually doesn’t hang on for 47 years, nor does it usually produce the intolerable symptoms you suffer.

DEAR DR. DONOHUE: These days I keep hearing “He or she is bipolar.” Would you please explain what that means? – N.W.

ANSWER: “Bipolar” has replaced “manic depression” to describe people who suffer mood swings from the heights of elation to the depths of gloom. It afflicts 1 percent of the population and generally comes on during the 20s or 30s. The cause is believed to be an imbalance in the brain’s chemical messengers that effect communication between the brain’s nerve cells. Medicines can keep most people with this illness on an even keel.

DEAR DR. DONOHUE: What is the life span of a pacemaker? – E.K.

ANSWER: It depends on how much voltage it has to deliver, and that, in turn, depends on whether it paces continuously or only intermittently and whether it paces more than one heart chamber. For most, the pacemaker battery has to be changed in about 10 years.

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.