DEAR DR. DONOHUE: A recent urinalysis indicated that I had a high protein reading. Just what does this indicate, and how serious is it? What can I change in my eating or drinking habits that would improve this? - D.D.H.

ANSWER: While a bit of extra protein in the urine is usually insignificant, sometimes it can be a serious sign, not one you want to leave hanging in the air.You want to know if you have proteinuria, the technical name for protein in the urine, all the time and just how much of it your urinary system is passing through in 24 hours. You want to know what this means, if anything, regarding the health of your kidneys.

Sometimes, protein in the urine is a passing thing. For example, a high fever can allow temporary escape of protein into the urine. In any event, no change in dietary habits will change the situation. You need a recheck to see, first of all, whether the reading was a temporary quirk or a sign of a chronic problem.

DEAR DR. DONOHUE: How about diagnosis of genital herpes? How about the blood test vs. the swab test? Which is best, doctor? - R.R.

ANSWER: Fluid swabbed from a herpes blister, then put into special material that allows the virus to grow if present provides the most certain diagnosis of herpes. Since this is rather impractical in most cases, a less refined test will do. Smears from the blister can be stained with dyes to permit quick and reliable diagnosis.

As for blood tests, they are reliable for first-time herpes infections, but are less so for infections that recur. For your other questions, I am sending on the herpes material. Others may order by writing Dr. Donohue/No.17, Box 830, Gibbstown, NJ 08027-9909, enclosing a long, stamped, self-addressed envelope and $2.

DEAR DR. DONOHUE: I am female, 36, and have noticed small white patches of skin forming on the bottom of each eye, under the lids. Why do these patches form in these places? My doctor had me checked for cholesterol the next week after I reported the patches, and it was very low - 158! Can they be removed cosmetically? - Mrs. H.D.G.

ANSWER: These are xanthelasma (ZAN-thu-LAZ-muh). They really are yellowish streaks of fat accumulation on the very thin eyelid tissue. Half the people with this sign do have accompanying high cholesterol and triglycerides levels. Why the sign occurs in those with normal blood fat levels has not been explained.

Xanthelasma are also seen in liver disease, diabetes and underproducing thyroid. I'm sure your doctor is looking into these possibilities. Let me know the results. Yes, if xanthelasma are a cosmetic concern, they can be removed. But there is no guarantee they won't return.

DEAR DR. DONOHUE: Why do children have to wear shoes? I think barefootedness is healthy. - Mrs. K.I.

ANSWER: Given a world free of toe stubbing, sharp rocks and other hazards, I might agree with you. But shoes are necessary inconveniences to keep children's feet unscarred, infection free, warm and comfortably cushioned.

DEAR DR. DONOHUE: I'm 35. I have episodes where my heart suddenly starts beating wildly. This usually stops as fast as it starts, lasting about eight seconds. I can stop an episode by coughing. My doctor has me on Inderal. I also have mitral valve prolapse. Is there any other medicine? - C.M.

ANSWER: Why don't you get your doctor to let you wear a portable heart monitor for a couple of days? That will tell exactly what's happening to your heart during the speedup episodes.

You seem to be having paroxysmal atrial tachycardia (PAT). It is interesting that your coughing aborts an episode. That involves a reflex nerve connection. The cough causes the heart-slowing nerve to kick in, aborting the attack.

Your medicine is commonly used to prevent such attacks. If it's not working, perhaps the dosage needs adjustment. Yes, there are other drugs to use, and if you report your episodes, perhaps your doctor will switch you to one.

As frightening as PAT can be, this is not usually a sign of serious heart trouble. Yes, people with mitral valve prolapse may also have such rapid heart episodes. I think it would make sense for you to use a heart monitor to find out just what is going on.

DEAR DR. DONOHUE: I have to have an injection of Rhogam in a few weeks, and I'm very worried. My doctor says it's safe from AIDS, but how can it be if it is a blood product, as they say? If you confirmed what my doctor says, I would feel much better. - M.S.

ANSWER: Rhogam is a form of gamma globulin. It is used to prevent problems in a baby when the mother has an Rh-negative blood type and the father's is Rh-positive.

I concur with your doctor. AIDS has never been traced to use of this or any form of gamma globulin. Nor has hepatitis.

We are all very conscious of AIDS and the potential for blood transmission. Great pains are taken to protect not only blood, but blood products. You can have your shot and not worry in the least.