DEAR DR. DONOHUE: My friend has an 11-month-old daughter who had an E. coli blood infection. The child shuddered once, was a bit lethargic, but felt cool to the touch. The digital ear thermometer registered normal. My friend’s instinct was to go to the hospital. The baby had a temp of 105. Are digital thermometers ineffective? – G.W.

ANSWER: “Digital” refers to the way information is displayed – in digits (numbers). A digital watch shows time as 10:02, for example, not with a large hand pointing to the minute and the small hand to the hour. The issue with thermometers is not how they display body temperature – digitally or not – but which body site gives the most accurate reading.

Rectal temperatures are subject to fewer vagaries than temperatures taken at other body sites, and the Canadian Pediatric Society recommends rectal-temperature-taking for children up to 5 years of age. It doesn’t matter if the temperature is displayed digitally or on a gauge with degrees.

Ear thermometers are accurate to within 0.2 F (0.1 C). They use infrared sensors to measure the heat given off by the eardrum and surrounding tissues. Placement can be a problem, especially with young children.

Plastic strips with liquid crystals are applied to the forehead to give a rough idea of body temperature. Their readings are affected by sweat, the surrounding air temperature and the finger temperature of the one applying and removing the strip. They should be used only for rough estimates.

For older children and adults, oral temperatures are reliable. Hospitals routinely take them, and the reading can be displayed digitally.

Your friend is blessed with common sense. Severity of illness should not be based on one finding – temperature, for example. A blood infection with E. coli can cause a drop in body temperature, and looking for a high temperature could be misleading. The baby’s temperature might have risen en route to the hospital.

DEAR DR. DONOHUE: I have been working on a deck for three weeks. I have developed a terrible pain on the thumb side of my left wrist. I am left-handed. I cannot hold a tool without pain. What is this? – K.N.

ANSWER: The first thought that comes to mind is de Quervain’s disease. It’s an inflammation of the tendons that control thumb motion. It’s also a narrowing of the compartment through which those tendons run to attach to the thumb.

Wrap the fingers of your left hand around your left thumb. Then, with your right hand, bend the left hand toward its little-finger side. If that motion hurts, that’s pretty good proof you have de Quervain’s.

It’s good you have laid down your tools, because rest is essential for cure. A splint might give you even greater rest. Anti-inflammatory medicines like ibuprofen can be helpful, if you can take them.

De Quervain’s is a common condition, and it happens to many people. People who spend hours scooping ice cream for hungry customers are often victims. So too are handshaking politicians.

Please realize that this is a guess on my part. If your pain doesn’t leave with a week of rest, then you have to see the family doctor. If your condition proves to be de Quervain’s but it has not responded to the above conservative treatment, a cortisone injection into the inflamed area greatly speeds the resolution of symptoms.

DEAR DR. DONOHUE: I am waiting to be called in for an oximetry test. Will you explain what that involves? – E. S.

ANSWER: You will be pleasantly surprised by the ease and complete lack of pain of an oximetry test.

A little device that looks a bit like a spring-loaded clothespin is clipped to your fingertip or earlobe. The device passes a beam of light through the tissues to determine the amount of oxygen in the blood.

The test is quick, with no fuss, no pain and no bother.

DEAR DR. DONOHUE: More than a year ago I found a lump on my neck. My doctor said it was a lymph node and that unless it got bigger or started to hurt, I should not be concerned. Recently a massage therapist noticed it. It has not become any bigger; if anything, it is smaller. Should I be concerned? – H.M.

ANSWER: The body has hundreds of lymph nodes, popularly called glands. They aren’t glands, and how that name found its way into general use I do not know. The nodes are located in strategic positions to filter out germs and any harmful material that makes its way into the body. A sore throat, for example, all but guarantees that neck nodes will get bigger and hurt.

Nodes enlarge for reasons other than infections. Illnesses like rheumatoid arthritis and lupus often lead to node enlargement. An overactive thyroid gland can cause nodes to grow. However, the greatest concern for an enlarged node or nodes is cancer, either cancer of the node itself (primary node cancer) or cancer that has spread to the node from a nearby organ. Primary node cancer is called lymphoma, and its two varieties are Hodgkin’s disease and non-Hodgkin’s lymphoma.

Distinguishing a cancer-enlarged node from a node that has gotten bigger due to a less serious cause can be difficult. Node size helps make the distinction. Nodes that are less than 1 cm (0.4 inch) wide and long are generally not dangerous. Nodes larger than 2 cm are often cancerous. Those in between are suspect and have to be watched carefully. Tender nodes usually indicate inflammation. Rapid growth is another sign of cancer.

Your node is small. It hasn’t changed in more than a year, so it’s most unlikely to represent cancer. You should be concerned enough to show it to your doctor when you are next examined. If there is any question of what it represents, it can easily be removed and inspected microscopically. That settles all questions on the nature of a large node.

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.