DEAR DR. DONOHUE: I was 16 when I was diagnosed with psoriasis. I am now 36 and still trying to get rid of it. My doctor prescribed Dovonex cream, but it isn’t working all that well for me. I eat right, get plenty of sun, take saltwater baths and moisturize daily. Does the immune system have anything to do with psoriasis? Do you know of any natural way to get rid of it? – J.M.

ANSWER: The immune system has a great deal to do with psoriasis, but let’s start at the beginning. Up to 3 percent of the population has to deal with this chronic skin condition. It appears at any age, but there are two age peaks when it most often appears – 22 and 55. The skin breaks out with red patches covered with silvery scales, and the patches might itch. Finger and toenails frequently thicken and have pits.

What has happened is a rapid turnover in skin cells – so rapid that immature skin cells migrate to the surface and try to do the work that a seasoned veteran should be doing. The immune system is at fault. It causes a release of chemicals that lead to the whirlwind ascent of young skin cells to the outermost skin layer.

You are living at a time when the number of psoriasis medicines is large and when control can be expected. Your Dovonex (a vitamin D relative) quite often successfully puts a lid on psoriasis outbreaks. If it’s not working, you shouldn’t stick with it. Cortisone-containing creams, ointments, foams and sprays are often successful. Ultraviolet-light treatments in conjunction with psoralen drugs can keep the skin psoriasis-free. New treatments include the biological agents Enbrel, Remicade and Humira, medicines that control the chemicals released by the immune system. No treatment can be considered a cure. They are effective controls.

Natural treatments also abound. Sunlight is one, but you must be careful not to get a sunburn and not to overdo it. Too much sunlight is responsible for skin cancer. Aloe vera, tea tree oil and apple cider vinegar, all applied to the skin, are examples of natural remedies. I can’t vouch for their effectiveness.

You won’t regret contacting the National Psoriasis Foundation. It keeps people up to date on the latest treatments. You can reach the foundation at 800-723-9166 or on the Internet at www.psoriasis.org.

DEAR DR. DONOHUE: I’m being badgered to eat more fish, which I do not like. I’ll do so if fish keeps me healthy. However, I’m also told that fish is full of poisonous mercury. That doesn’t sound like an endorsement for fish. What’s the true story? – G.D.

ANSWER: The true story is that fish is good for health. It’s high in protein and low in fat. It contains omega-3 fatty acids, which promote heart health, protect against strokes and guard the heart from developing abnormal beats.

Fish that have the highest concentrations of mercury are shark, swordfish, tilefish and king mackerel. People should not eat these fish frequently, and pregnant women, nursing mothers and young children should avoid them.

Two fish servings a week are recommended for the rest of us. A serving is 6 ounces.

DEAR DR. DONOHUE: I would like to ask you an important question. What is lichen sclerosus? What causes it? Is it treatable? What effect does it have on a young woman of childbearing age? – B.U.

ANSWER: Lichen sclerosus is a skin condition where patches of skin turn white, become thin, crinkle up and itch or burn. The patches look somewhat like cigarette paper. Most often, lichen sclerosus appears on the genital skin and can make intercourse painful. When it occurs before puberty, as it can, it frequently disappears after puberty takes place.

No one is positive about the cause, but it may be that the immune system has targeted the skin as a foreign invader.

It is treatable. Clobetasol, a cortisone ointment, brings relief to about 80 percent of patients. Testosterone cream also works. I’ve made it sound like it’s easy to treat. It is not. It requires perseverance.

A woman of childbearing age has the same symptoms that affected people of any other age have.

DEAR DR. DONOHUE: I have been eating and enjoying grapefruit and grapefruit juice all my life. People say it is not good for you. What’s wrong with it? I am 91. – M.R.

ANSWER: There’s nothing wrong with grapefruit. It’s good for you. It’s a source of vitamin C and vitamin A. It contains calcium and potassium. A half of a grapefruit has only 40 calories. You can’t find as good a nutritional bargain in many places.

I toast your health with grapefruit juice. You should do the same.

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