DEAR DR. DONOHUE: You never mention the many causes of vertigo. I was diagnosed with benign positional vertigo and was given a pill that made me sleepy. A few weeks later, I had some bad falls and sustained fractures. I had an appointment with my oncologist, who ordered MRIs that showed the fractures. The oncologist sent me to an ear, nose and throat doctor, who found an ear imbalance, which he corrected. Now, instead of the constant fear of moving around, I am myself again. I feel it is important for people to be aware that there are different kinds of vertigo, with different treatments. – R.C.

ANSWER: There are more than 10 causes of vertigo – dizziness that’s a spinning sensation. It’s not a sensation of feeling faint or of lightheadedness. Those are other problems.

Many of the causes of vertigo are found in the inner ear, where our balance organs are located. In benign positional vertigo, there’s a displacement of particles from their normal position in the inner ear to other ear structures. That displacement causes vertigo when the head moves. Rolling over in bed makes people with this condition very dizzy. Often, through a series of head movements in the doctor’s office, this dizziness can be cleared.

Inflammation of the inner ear is another big cause of vertigo. It’s called vestibular neuronitis, or labyrinthitis. A virus is the cause of the inflammation. Time cures this kind of vertigo, but it can take six weeks or longer for the dizziness to leave completely. Prednisone can often hasten the process. Antihistamines like Phenergan can also be helpful, but they do make people drowsy. Perhaps that was the pill you took.

Head trauma can disrupt the workings of the inner ear and bring on vertigo. So can Meniere’s disease, episodes of hearing loss, dizziness and ear noises. People recover after an attack, but recurrences are the rule, and symptoms tend to become permanent in time. A very-low-salt diet is one way to treat this condition.

The side effects of many medicines, interruption of the blood supply to the brain, multiple sclerosis and a disruption of the chain of bones in the middle ear are other causes of vertigo. Each has its own treatment.

The vertigo booklet discusses this prevalent malady and its treatment. To order a copy, write: Dr. Donohue – No. 801, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order (no cash) for $4.75 U.S./$6.75 Can. with the recipient’s printed name and address. Please allow four weeks for delivery.

DEAR DR. DONOHUE: I am devastated. My job is to draw blood. Yesterday I was stuck from a needle used to draw blood from an HIV-positive person. How high is my risk of catching HIV? – W.A.

ANSWER: The risk of coming down with AIDS from a needle stick contaminated with the HIV virus is 3 in 1,000. That’s an estimate. The actual risk depends on how much blood was on the needle and how deep was the stick.

You should be tested for AIDS immediately and again six weeks, three months and six months after the date of the stick.

In every place where blood is drawn, there should be a copy of the Centers for Disease Control and Prevention’s recommendations of what to do in these circumstances. One course of action, depending on the circumstances, is to initiate preventive therapy. You should talk to your supervisor about this as soon as you can.

DEAR DR. DONOHUE: For the past four years, a spot on my back has itched. I scratch it all the time. The skin where I scratch is turning dark. Why? – M.

ANSWER: Have you a diagnosis for the itchy spot? If not, get one. That’s the only way of addressing this issue sensibly.

Scratching turns the skin thick and leathery. The skin often darkens in color too. You can return the skin to its natural state by not scratching. I know how difficult that can be. The relief scratching gives is beyond words, and the annoyance of an itch is also beyond words.

You’ll solve this problem only by seeing a skin doctor.

DEAR DR. DONOHUE: I have scabies. I feel like I have received a jail sentence. I saw one doctor three times without getting a diagnosis. The dermatologist put me on Acticin. After one application, the itch has gotten worse. How can I prevent myself from reinfection? When am I safe to go out again? This is a nightmare. I have been washing my linens, spraying the bedding and vacuuming, but I don’t want to spend the rest of my life doing this. Please address this. I have already infected tons of people because this is so highly contagious. I had breast cancer, but this is worse because it’s so vague. – A.T.

ANSWER: Take a deep breath. Scabies isn’t one-quarter as bad as you imagine.

The female scabies mite is barely visible, only .35 millimeters long. One millimeter is .04 inches. She burrows into the skin and makes a short, serpentine tunnel in which she lays her eggs. The tunnel looks like a thin, red line.

You haven’t infected tons of people. It takes close contact with another to transfer the mite. In rare instances, when a person is heavily infected, bed linen or clothes could be a source of transmission, but truly, that seldom happens.

The scabies mite survives only 24 to 36 hours when it leaves human skin. So you have reassurance that in two or three days, any mites on furniture or other inanimate objects are dead. You can put your vacuum and sprayer away. Washing bedding or clothing in hot water and drying them on the hot cycle of a dryer kills the mite. You’ve done that.

Acticin (permethrin) is standard treatment for scabies and is almost always effective. The increased itching after applying it comes from an allergic reaction due to the death of the mites. An antihistamine can take care of the itch. Itching might not subside for several weeks after a person is scabies-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