QUESTION: I am 34 and have hip arthritis. I want hip replacement, but my doctor wants to delay surgery because of my age. He says that waiting will provide maximum benefit from the new hip. I wonder how I can get information on the progress being made in hip replacement surgery. I am eager to have a functional hip sooner rather than later but do realize the limited lifespan of the replacements. - L.S.

ANSWER: I have an address for you, but first let me comment on replacement surgery in general. You don't have to be an older person to have the replacement surgery. Age does become a consideration for some very practical reasons. You should discuss this.Hip joints last on average 15 to 20 years. You are only 34, which means you might face the need for a second, even perhaps a third replacement during your lifetime. This is the point your doctor is making in urging delay. Were you crippled to the point of immobility, for example, that would probably cancel out the age factor. Apparently this is not the case.

Hip replacement procedures are constantly being upgraded and improved. Newer cementing agents guard against replacement joint loosening, and a new procedure permits replacement entirely without cement. In it, the joint is fashioned so that adjacent live bone and the artificial material merge naturally.

For a free brochure on joint surgery, write the Arthritis Foundation, Box 19,000, Atlanta, GA 30326, or call 1-800-283-7800. Also there is a review of the artificial joint scene in the Sept. 13, 1990, issue of the New England Journal of Medicine (Vol. 323, No. 11, p. 725).

QUESTION: I'd appreciate any information on Schamberg's disease. - H.L.

ANSWER: Schamberg's disease is marked by a peculiar skin rash - red pinhead-size spots. Dermatology texts liken the rash to grains of Cayenne pepper sprinkled on the area, usually the lower legs.

The rash results from an inflammation of the body's tiniest vessels, the capillaries, specifically those of the skin. There usually is no itching involved, and the tiny spots often, but not always, fade within three months. Meanwhile, cortisone creams, even cortisone by injection, are sometimes used to control the inflammation.

I know an unasked question here has to do with cause. We don't know what lies behind the vessel inflammation.

QUESTION: About a year ago, my 17-year-old daughter started getting hives when she took a shower. We changed soaps and washed clothes in different detergents, and she has tried using different water temperatures. The hives last half an hour to an hour. What could cause this to happen? - M.H.

ANSWER: She could have cholinergic urticaria, a fancy term describing nerve-related hives arising from events such as warm showers, hot climate, exertion, or emotional stress. "Cholinergic" refers specifically to acetyl choline, a substance released at nerve fiber endings as impulses pass through. Excess amounts of this substance can lead to the kind of situation you describe.

Now, there is a rarer form of hives that comes when the body is exposed to water, no matter what its temperature. But this is so rare, I'd tend to dismiss it as figuring into your daughter's condition.

I suggest your daughter take baths in tepid water for a while, giving that a chance. If this proves futile, then she should ask her doctor if he wants to prescribe antihistamines as a preventive.

Arthritis sufferers can be helped. For a copy of Dr. Donohue's booklet No. 2, "How You Can Control Arthritis," which discusses many types of arthritis and related joint diseases, send your request to Dr. Donohue/No. 2, P.O. Box 830, Gibbstown, NJ 08027-9909. Enclose a long, self-addressed, stamped envelope and $2.

Dr. Donohue welcomes reader mail but regrets that, due to the tremendous volume received daily, he is unable to answer individual letters. Readers' questions are incorporated in his column whenever possible.