QUESTION: My beautiful granddaughter, 22, had a melanoma mole removed from her shoulder, just under where the bra strap is. She has been an avid bowler, which does involve considerable irritation at that spot. I wonder if irritation can cause a melanoma. Enlighten me please. - E.M.

ANSWER: We don't usually think of skin irritation as a cause of melanoma, although I did find one source that says areas of irritation, such as under belts or straps, may be more prone to this skin cancer. Now, melanoma may develop from what we call a dysplastic nevus, which can easily be mistaken for a common mole. Dysplastic nevus, an irregular-shaped multicolored mole, is found in non-sun exposed areas. This just might be the background of your granddaughter's.Fair skin, excessive sun exposure (particularly at high altitude or in tropical areas) and having a history of it in the family are the usual factors common to melanoma. I'm glad you give me a chance to review the melanoma story. It allows me to stress that this type of cancer can be prevented with simple preventive steps or successfully treated if recognized early. We've seen a twelvefold increase in melanoma in the past 60 years.

The easiest way to learn melanoma detection is by the "ABC" method. "A" is for asymmetry. If you were to draw an imaginary line at the midline of a melanoma, the two halves would be different in shape. "B" is for border. It is scalloped or notched and a bit fuzzy. "C" is for color. The melanoma tends to an unevenness of color, a mixture of grays, browns and blacks. Now add an "S" - for size. Any brownish patch wider than pencil eraser width should be suspect.

QUESTION: I have been a diabetic for 33 years. I have read that taking vitamin C in large doses can alter test results for diabetics. Does this apply to blood tests or, to urine tests, or both? - J.M.R.

ANSWER: Vitamin C does not interfere with blood sugar tests. In large doses, it can cause false results in urine sugar tests. It depends on the test used. Some will show falsely negative for sugar and some falsely positive. If you had given me the name of the test you use, I could have told you which result to expect. But I'll bet if you read the instructions carefully, that information will be supplied.

QUESTION: My 12-year-old son has been recently diagnosed as having spondylolysis in his back. Could you explain this diagnosis in layman's terms? Will this get worse as he grows older? How will this affect his sports participation? - C.B.

ANSWER: Each individual spine section (vertebra) has a bony arch over it. Spondylolysis is a crack in an arch section. His doctor can be more specific, but often such a crack develops from a jarring of a somewhat thinner-than-usual arch.

Again, I must defer to his own doctor. However, there's no question but that he should stop sports participation until all pain has gone. That usually takes about a week. After that, he must restrict activities that provoke pain or that have been specifically forbidden by the doctor based on the scope and severity of the problem.

Spondylolysis doesn't have to get worse with age. Olga Korbut, the world-famous gymnast, had spondylolysis and continued her career without any major interruptions.

Want to get into shape? Dr. Donohue's booklet No. 12, "Introduction to Fitness," offers a fitness program anyone, regardless of age, can adapt. For a copy, send your request to Dr. Donohue/No. 12, 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.