This month, Dr. Sydney Spiesel discusses peanut allergies, the stubbornness of dust mites, how breast-feeding may help prevent diabetes, and the fallout from a toxic spill in China. (Click here and here for the last two roundups.)
Kissing: Peanut alert.
State of the Science: Between 6 percent and 12 percent of people who are intensely allergic to peanuts report that they've had a reaction after kissing someone who has eaten peanuts as many as six hours beforehand. Usually, the result is skin irritation, blistering, or swollen lips. But this week, a 15-year-old Canadian youngster with a peanut allergy died after kissing her boyfriend, who had just eaten a peanut-butter sandwich. She collapsed as a result of anaphylactic shock, the most intense form of allergic reaction. Appropriate treatment with injected epinephrine failed to save her.
Prognosis: It's estimated that about 100 peanut-allergic people die annually in the United States after accidental exposure. The mechanism of peanut allergies is similar to that of other allergies, but the effects tend to be worse. And peanut allergies are less likely to fade with time than most other food allergies. The fuss over peanuts is justified. Here are steps we should take to prevent sad accidents:
- Restaurants should never use peanut butter as a "secret ingredient" and should probably indicate the presence of peanut- or tree-nut-containing foods on their menus.
- Schools need to think out policies that restrict or forbid peanut products in the lunchroom. School nurses should be trained and prepared to deal with life-threatening allergic reactions.
- Seriously allergic children should be trained about how to avoid risk. They should also at all times carry epinephrine autoinjectors (EpiPen is the major brand for this product) and an antihistamine like Benadryl. Both should be taken at the first inkling of exposure. Most patients should not wait to see if the treatment is effective because if it isn't working, they will be in big trouble. Instead, a fast trip to the emergency room is in order.
- Oh, and significant others shouldn't munch on peanuts or their products for several hours before they kiss their allergic good friends.
Dust Mites: Why we're stuck with them.
More allergens: If you are allergic to anything at all, you are probably also allergic to cats, dust, or both. I don't mean cats themselves or even their dander (shed flakes of dead skin). I mean cat spit. As you've probably noticed, cats constantly lick themselves. Many humans—perhaps most—are intensely allergic to a saliva protein that dries on the cat's fur. We inhale microscopic particles of this protein, and it makes us wheeze.
The most significant allergen in dust comes from the bodies and droppings of dust mites. These mites are microscopic creatures, similar to insects but more closely related to spiders (they have eight legs instead of six and don't fly). They're too tiny to see unless they are floating in air and illuminated by a bright light against a dark background. They live in fibers, preferring the natural to the synthetic. They mainly subsist on the tiny flakes of skin that are constantly falling off us—their Latin name means "skin eaters." Dust mites stimulate an asthma attack in many people when they're inhaled, after we've raised them into the air simply by walking on a carpet or dropping into bed.
The fight: It's not easy to get rid of mites. Conventional wisdom has recommended vacuuming them up with special (and expensive) HEPA vacuum cleaners. Ordinary vacuum cleaners suck up the mites but can't then strain out their minute bodies, so the mites that are vacuumed just blow back into the room. It turns out, however, that this is only a small piece of the problem. In a funny way, vacuuming—even HEPA vacuuming—actually causes the dust-mite problem.
State of the Science: A wonderful and long-neglected study by Dutch researcher D.P. Wassenaar, working in the Department of Dermatology of the University Hospital in Utrecht, tried to determine how much vacuuming it would take to clear dust mites out of carpets. Wassenaar filled a laboratory with carpets, which were frequently and repeatedly vacuumed with a powerful machine. Early on, no matter how much vacuuming was done, the daily mite yield remained pretty much constant. But as time went on, the yield went way, way up. How?
Prognosis: Solving the mystery turned out to be a matter of shifting focus. The researchers had to pay attention not to the dust mites, but to the Cheyletus mite, which preys on dust mites but doesn't grip fibers as well. A good vacuuming got rid of most of the Cheyletus mites. But it didn't much reduce the dust mites. And with fewer predators, these mites were free to multiply like crazy.
Next, Wassenaar tried to wash out the dust mites, performing an "aqueous extraction" of the rugs (you and I might call it carpet shampooing). That really increased the dust-mite yield: The moisture apparently caused thousands of dust-mite eggs to hatch.
Lesson: The standard methods for abating dust mites can have the opposite effect that's intended. It's a reminder that we should be careful of simple and obvious solutions, which can have unwanted side effects or consequences.
Breast-Feeding and Diabetes: A benefit for mothers.
State of the Science: Usually, research on breast-feeding centers on effects on the baby. An exception is the recent report in the Journal of the American Medical Association by Dr. Allison Stuebe of Brigham and Women's Hospital in Boston. Stuebe and her co-workers examined the records of about 150,000 nurses and followed their health status for up to 16 years. They wanted to see if there was a relationship between breast-feeding and the development of maternal diabetes.
Prognosis: Most of the time, such statistical relationships—if any are found at all—are so small and subtle that it takes great faith to believe in them. Stuebe's study is exceptional in this way, too. The research clearly shows a substantial association between breast-feeding and a decreased risk for mothers of developing Type 2 (or adult onset) diabetes. Each year a mother spent breast-feeding an infant lowered her risk of developing diabetes by 15 percent. Breast-feeding for more than six months seems to have made the greatest difference.
Caveat: The benefits didn't extend to mothers who were already exhibiting signs of diabetes during pregnancy. And we don't actually know whether the process of extended lactation itself changed the mother, or whether the reasons that mothers breast-feed for an extended length of time somehow also mitigate the likelihood of diabetes development. But the authors took great pains to rule out extraneous factors, and a close reading of the report inclines me to think that the relationship between breast-feeding and diabetes prevention is causal. The authors present a possible explanation: They posit that the hormonal and calorie-consuming effects of lactation may lower the mother's blood-sugar levels. Lowered blood sugar is known to decrease the risk of diabetes. That mechanism is plausible, though far from proven. Still, we have another argument, this time from the mother's side, for breast-feeding.
Benzene: China's toxic mess.
The Mess: On Nov. 13, an explosion at a petrochemical factory, near the banks of the Songhua River deep in China, released into the river about 100 tons of toxic materials, much of it benzene. A 50-mile-long slick moved downstream. It's not known how long the managers of the chemical plant, operated by a subsidiary of the state-owned China National Petroleum Corporation, waited before informing local officials of the danger to downstream residents. But it was 10 days before the information became public, and then only because the water supply of Harbin, a city of more than 9 million, was turned off for five days.
State of the Science: Benzene is an organic compound with many important industrial uses. Its ring-shaped molecule is an important starting material for the production of plastics, artificial fibers, dyes, agricultural chemicals, and pharmaceuticals. It is added to gasoline to increase the octane level (thus helping the environment by eliminating the need for gasoline producers to incorporate lead in their product). Benzene was formerly used as an industrial solvent, but because the chemical is so toxic, that use has become less common.
The effects: Benzene is easily absorbed by the body if it is ingested or inhaled. It can also be absorbed through the skin. Inhaling high concentrations will make you dizzy and confused and cause you to stagger, as if drunk, when you walk. But the most serious benzene poisoning is not the effect of acute exposure on the central nervous system. It is the result of chronic exposure to lower concentrations. Over time, the liver converts absorbed benzene into toxic products that are especially harmful to the bone marrow, the site in the body where blood cells are produced. This exposure turns down or switches off the production of various blood cells. The result can be profound anemia (because there are not enough red cells to carry oxygen from the lungs to the tissues), vulnerability to infection (because the white cells that defend us are suppressed), and bleeding problems (because of the disappearance of platelets, which play a critical role in blood clotting). The damage to the bone marrow resembles the effect of radiation and, like radiation, often results in the development of leukemia.
Prognosis: What will this disaster mean to the populations exposed to this enormous toxic spill? These are the effects we can expect to see: chronic exhaustion from anemia, weakened ability to fight off infection, a propensity toward bleeding disorders, and a high rate of leukemia. All this could have been avoided or at least mitigated had officials focused more on environmental protection and quickly disclosed and addressed the accident.