DEAR DR. DONOHUE: I have drenching night sweats, so much so that I have to get up and change my nightclothes. I don’t feel ill, and my energy is good. Do these sweats indicate illness? What can I do for them? – I.J.

ANSWER: Most often, night sweats are not a sign of serious illness. Usually they result from the bedroom environment. It might be too humid. There’s a roundabout reason why that causes night sweats. Body temperature peaks around 4 p.m. and hits a low point around 4 a.m. The early-morning dip in temperature is partly achieved by loss of body heat through the evaporation of sweat. If the air has too much water in it, sweat doesn’t evaporate but drips off the body in rivers.

In cold climates, people might pile up too many blankets because the bed is cold when they climb into it. In time, body heat warms the bed, and the surplus of blankets raises body temperature and brings on sweating.

Sleepwear can be the root of the problem. Some fabrics seal heat and sweat on the body surface. A change might eliminate the problem.

Check the room’s humidity. If it’s high, get a dehumidifier or, at least, a fan. Turn down the heat in the room. Don’t use as many blankets. If these changes don’t lessen sweating, then you have to explore other possibilities.

Medicines can sometimes turn on sweating. Aspirin, some antidepressants and propranolol, used for blood pressure and heartbeat control, can do so. Alcohol and nicotine are other potential causes. Don’t drink alcohol after 3 p.m.

In a handful of instances, illnesses are the cause. Diabetes, neuropathies (nerve maladies) and a rare tumor called pheochromocytoma lead to sweating without raising body temperature. Heart valve infections (endocarditis), lung infections and some cancers, such as lymph node cancers, raise body temperature and produce night sweats.

DEAR DR. DONOHUE: In the past two weeks I have noticed on three occasions that there was blood in my ejaculation fluid. What causes this? Cancer? – L.Q.

ANSWER: Believe it or not, this is one of the most frequently asked questions I receive. The writer always wonders about cancer.

Hippocrates, the Father of Medicine, lived about 2,500 years ago and was the first person to describe this condition, which has the medical name of hematospermia – blood in the seminal fluid. Most of the time, it comes from the breakage of a small, superficial blood vessel in the genito-urinary tract.

If a man has any other symptoms, such as pain, or if the bleeding doesn’t stop within four weeks, then it can be a sign of trouble. Infections of the prostate gland, prostate enlargement and cancer could cause bleeding.

Men who take a daily aspirin or who are on the blood thinner Coumadin are likely to have hematospermia. You should mention this to your doctor, who can give you assurance of the innocence of hematospermia without a whole lot of fuss.

DEAR DR. DONOHUE: When I am in bed, I can hear my heart beating. I believe I am in good health, but this drives me crazy. What causes this? – B.N.

ANSWER: With even a slight bit of hardening, arteries close to the ear can produce a pulsating beat in the ear. This is usually the consequence of aging, and the only thing to do about it is to follow the incessantly preached exhortations to lower the fat and cholesterol in the diet, exercise, lose weight if necessary and keep blood pressure under control.

See if changing your sleeping position puts an end to the noise. You can also try keeping the radio on, not so loud that it prevents sleep but loud enough that it blots out the pounding noise in your ear.

Some truly serious problems can also produce the noise — partially obstructed neck arteries, blood vessel tumors, anemia and Paget’s bone disease. On your next visit, mention this to your doctor.

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.