DEAR DR. DONOHUE: My sister-in-law has just been diagnosed with interstitial cystitis. Neither of us has ever heard of it. Is it rare? She says there is only one medicine that can help, and it makes your hair fall out. Needless to say, she is very upset. Will you explain what it is and whether there is anything else she could take? – E.G.

ANSWER: Interstitial (IN-tur-STISH-ul) cystitis isn’t rare, but often enough, it isn’t recognized. Its main symptoms are intense bladder pain and frequent trips to the bathroom to empty the painful bladder. Those trips can be as many as 60 in one 24-hour interval. Women are affected more often than men, but men are not immune to it.

Apparently, the protective bladder coating has become defective, and urine penetrates to the bladder lining, causing great pain.

Almost as a rule, the signs and symptoms of interstitial cystitis are diagnosed at first as a bladder infection, and people are given antibiotics for treatment. Antibiotics do no good at all.

Your sister-in-law has much to be grateful for. She has been diagnosed, and appropriate treatment can be started. There is only one FDA-approved medicine for this condition. It’s Elmiron, which helps reconstitute the protective bladder layer. It doesn’t always cause baldness, and when it does, usually there is only a bald patch. There are other treatments. Amitriptyline, an antidepressant, is used not for its action against depression, but for its ability to ease pain. Gabapentin, a seizure control medicine, also is used for control of cystitis pain.

Your sister-in-law will do herself a world of good by contacting the Interstitial Cystitis Association for information and for keeping apprised of the latest treatments.

Its phone number is 800-HELP-ICA, and its Web site is www.ichelp.org.

DEAR DR. DONOHUE: I am a 61-year-old woman. I saw an OB/GYN doctor for genital itching. He prescribed Premarin cream, but the itching got worse.

Finally, a diagnosis of lichen sclerosus was made. Please enlighten me. I had never heard of it. Is it a fungus? Where did I get it? What is the meaning of “sclerosus”? – B.H.

ANSWER: Lichen sclerosus is not an uncommon disorder. It usually occurs in women older than 50, but it can appear at any age, and men can get it too. Most often, genital skin is involved. The initial breakout consists of shiny, small, white spots that itch or sometimes hurt. This then evolves into large, white patches. Itching can be intense. The skin thins and becomes fragile. It tears, bleeds and scars. Intercourse is often difficult.

Treatment consists of strong cortisone ointments, ones that can be obtained only with a prescription. These ointments are usually successful. People may have to continue ointment use less frequently once the condition is controlled so that it doesn’t recur.

Lichen sclerosus deserves a name change. “Lichen” does mean “fungus,” but this is not a fungal infection. Sclerosus (also spelled sclerosis) is a hardening, and the word refers to the hard scar tissue that forms if this condition goes untreated.

DEAR DR. DONOHUE: In the past few weeks, there have been a couple of letters to you regarding urinary tract infections. In your responses, you have not mentioned cranberry juice, and I find that surprising. I know from previous experience that cranberry juice works wonders for urinary tract infections. – D.B.

ANSWER: Cranberry juice can keep the most common bacterial cause of urinary infections from holding onto the bladder wall. It is flushed out in the urine. It is a valuable preventive and sometime treatment for bladder infections.

The booklet on urinary tract infections discusses this common illness in detail. To obtain a copy, write: Dr. Donohue – No. 1204, Box 536475, Orlando, FL 32853-6475. Enclose a check or money order for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Allow four weeks for delivery.

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