DEAR DR. DONOHUE: Please devote an article to staph infections. I thought they were hospital-related, but I find that’s not so. I just recovered from a staph infection on my entire arm. Several of my friends have had the same infection on different locations – fingers, knees, rear end. Can staph be transmitted via mosquitoes or pets? – D.T.

ANSWER: “Staph” is short for “staphylococcus” (STAFF-ill-oh-KOK-US), a bacterial germ found just about everywhere – on clothes, bedding, doorknobs, you name it. However, people usually catch it from another person, and most often that person carries the germ without any signs of infection. Mosquitoes aren’t known to pass it, and pets, if they ever do so, do it rarely.

Staph germs bombard us daily. For the most part people shrug them off. In a few, they cause infections like boils or styes. In still fewer they cause serious infections such as yours, and in a very small number they bring on infections that are matters of life and death.

The skin is not the sole site of infection. Staph can target bones, joints, heart valves and even the bloodstream. The last is a medical emergency.

Staph is also responsible for a common kind of food poisoning, the kind that comes on quickly, in a matter of hours, after eating contaminated food. Nausea, vomiting and, in many cases, diarrhea occur.

In the early days of antibiotics, penicillin took care of most staph infections. The germ learned how to dodge ordinary penicillin, and specially formulated penicillins were devised to kill it. Some staph, called MRSA staph, have become resistant to those penicillins, making infections with MRSA staph difficult, but not impossible, to cure.

People with repeated staph infections often have a place on their bodies where staph have found a safe haven – inside the nose, for example. Eradicating those sanctuaries can stop the cycle of infections.

DEAR DR. DONOHUE: I have a Baker’s cyst on the back of my right knee. It is painless. Now one is forming on the back of my left knee. What causes this? – F.R.

ANSWER: A Baker’s cyst is a soft, behind-the-knee bulge that is actually a swollen bursa. Bursas are disks that the body uses as ball bearings, reducing friction that comes when tendons rub against bones.

The behind-the-knee bursa that becomes a Baker’s cyst is connected to the knee by a tunnel that has a one-way valve. If there is any trouble in the knee joint that promotes an increased production of joint fluid, the fluid makes its way into the bursa. The one-way valve in the connecting tunnel closes, and the fluid cannot escape from the bursa. It swells.

A Baker’s cyst, therefore, generally indicates trouble in the knee. Knee cartilage might be torn, or there might be some arthritis in the knee joint.

If the knee or the Baker’s cyst doesn’t hurt, then matters can be left alone. The only big trouble that might occur – and this doesn’t happen too often – is for the cyst to break. That does hurt. If the doctor can treat the knee problem that’s leading to overproduction of joint fluid, then the problem ought to resolve. If a treatable knee problem cannot be found but the cyst is kicking up trouble, the doctor can drain fluid from it and inject one of the cortisone drugs to prevent fluid from re-accumulating.

DEAR DR. DONOHUE: Two months ago I woke up feeling fine, but then everything suddenly disappeared from my memory. I am told I kept repeating the same words to myself. I had a CT scan done. Nothing was found, and my memory gradually returned. I was diagnosed as having had transient global amnesia. What can you tell me about it? – P.W.

ANSWER: Transient global amnesia is a sudden period of disorientation that lasts for a few hours to two days. During the interlude, people are at sea, asking over and over where they are, what’s happening and even who they are. During the episode they are alert and able to speak but remember nothing. The cause remains a mystery. However, an attack does not put a person at risk for a stroke.

DEAR DR. DONOHUE: Should you take a multivitamin before, during or after you eat? I have conflicting information. Some say if you take it with food, the vitamin is not absorbed. Others say if you take it on an empty stomach, the vitamin passes through your digestive tract too fast. Who is right? – A.H.

ANSWER: I’m not sure that it makes a great deal of difference when you take it.

I’ll give you what I believe is the majority opinion. It says to take a multivitamin after eating, because food in the stomach delays the vitamin’s passage through the intestinal tract. That gives it a chance for complete dissolution and absorption.

DEAR DR. DONOHUE: My problem is blushing – to the extent that I am all but housebound. My problem mostly occurs when I’m out somewhere and come face to face with a handsome man. It happens at other times, but rarely. What can I do? – O.R.

ANSWER: Dilation of arteries fills them with blood, and that turns the face red. Let me give you some rare but important causes of blushing. Carcinoid syndrome and pheochromocytoma are two tumors that release substances that dilate facial blood vessels and bring on a blush. A thyroid gland tumor is another cause of blushing. Panic attacks can spark a blush.

Your blushing is mostly related to a social situation, and that argues against any physical cause for blushing, since physical causes bring on a blush at any time and under any circumstances. Yours is a psychologically induced blush, and the reasons why it happens are buried somewhere deep in your subconscious.

Speak with your doctor. You might want to try a beta-blocking drug, such as Inderal, which can sometimes prevent blushing.

Biofeedback, taught by a professional, is a process that helps people gain a degree of control over spontaneous, involuntary body reactions. It could be a way for you to gain mastery over your blushing.

For blushing that turns a person into a hermit, surgical procedures exist that cut nerves that regulate facial artery expansion. Thoracic surgeons or neurosurgeons are the doctors who do this kind of surgery.

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.