Spring and fall are peak allergy seasons in many areas, with spring trees still pumping out millions of grains of pollen each day and the summer grasses already starting to contribute their share. Sneezing, running nose, and itching – itchy eyes, itchy nose, itchy throat – wouldn't it be great to be able to prevent allergies before they even got started.

Preventing asthma and allergies is possible, according to a study in the June 2003 issue of Thorax. Children at high risk for asthma and allergies were recruited in 1990 to be part of this study. Half of them went about life as normal, and the other half had a low-allergy diet as infants – starting with breast milk (with moms on a low-allergy diet) or Nutramigen formula (no milk or soy-based formula). This group of families also undertook significant measures to avoid exposure to house dust during infancy.

Avoiding inhaled allergens, though, may be another story. Other studies have shown that babies who are exposed to dogs and cats before the first birthday, for example, are far less likely to develop allergies later. It seems to me that the nose is designed to detect changes (which is why you often no longer notice even very strong odors if you are around them long enough). It seems to me that a baby’s nose learns what is "normal" to have around them in the air during the first year or so, and then begins to consider some later arrivals as dangerous invaders – the body develops an allergic response to them.

Allergies happen when the body is tricked into thinking that harmless particles are dangerous invaders. The immune system tries to get rid of these allergens by sneezing them out, flushing them out with tears or mucus, or dislodging them with nose rubbing. It tries to prevent them from getting into the lungs by constricting the airways. These are all normal responses to toxins and viruses. They are allergies if the trigger is not really a problem.

There may have been other differences between the two groups in the study. One half certainly worked harder and paid more attention to allergy issues. We still have a lot to learn. What’s exciting about this breakthrough study is that it demonstrates that preventing allergies, asthma, and eczema is truly possible. Now we just have to learn how best to do it.

This is a type of nuclear scanning test or myocardial perfusion (mi"o-KAR'de-al per-FU'zhun) imaging test. It shows how well blood flows to the heart muscle. It's usually done along with an exercise stress test on a treadmill or bicycle.

The thallium stress test is useful to determine:

- Extent of a coronary artery blockage

- Prognosis of patients who've suffered a heart attack

- Effectiveness of cardiac procedures done to improve circulation in coronary arteries

- Cause(s) of chest pain

- Level of exercise that a patient can safely perform

- If the test is normal during both exercise and rest, then blood flow through the coronary arteries is normal. The coronary arteries supply blood to the heart muscle.

- If the test shows that perfusion (blood flow) is normal during rest but not during exercise (a perfusion defect), then the heart isn't getting enough blood when it must work harder than normal. This may be due to a blockage in one or more coronary arteries.

- If the test is abnormal during both exercise and rest, there's limited blood flow to that part of the heart at all times.

- If no thallium is seen in some part of the heart muscle, the cells in this part of the heart are dead from a prior heart attack. (They have become scar tissue.)

The first pictures are made shortly after the exercise test and show blood flow to the heart during exercise. The heart is "stressed" during the exercise test -- thus the name "stress test." The patient then lies quietly for 2-3 hours and another series of pictures is made. These show blood flow to the heart muscle during rest.

Sometimes you can't do an exercise test because you're too sick or have physical problems. In this case, a drug such as dipyridamole (di-pi-RID'ah-mol) or adenosine is given. This drug increases blood flow to the heart and thus "mimics" an exercise test. Then the thallium test is given.

Most people can raise their HDL (good cholesterol) levels by exercising, not smoking and staying at a healthy weight.