John Lawton

Looking for a better way to say "Shoo, fly"?Jonathan Day, Ph.D., a professor of medical entomology at the University of Florida, tested popular bug repellents on 20 crazy volunteers—each willing to submerge his or her arm into a cage of swarming mosquitoes for one minute at regular intervals. Day then determined each lotion's average protection time (how long it took to get three bites); he found that products containing deet worked the longest. But that doesn't make them the best: in very high doses, deet can cause seizures. Day, along with the American Academy of Pediatrics, suggests sticking to products whose deet concentration is 10 percent or less. He also recommends avoiding sunscreen-and-repellent combinations on kids; parents fearing sunburn tend to apply both, deet and all, far too often. If you'd rather avoid chemicals altogether, reach for one of the natural alternatives with citronella. They're just as effective as deet, but evaporate faster. Oils—mineral, soybean, anise—also work. "Mosquitoes just don't like the slick feel of the stuff," Day says. So the theory about Avon Skin-So-Soft (made with mineral oil) is true—though if you baste yourself for full protection, your skin may not feel so fab.

When the mercury rises, more than 68 million Americans flock to water parks to splish-splash away the heat, but it's not all fun in the sun. Over the past nine years, the Centers for Disease Control has documented a 150 percent increase in the number of people contracting waterborne infections—some fatal—from shared swimming waters. The bacteria come from fecal matter that has made its way into the water through a leaky diaper or residue. . . let's just call it a bad wipe. Once the bacteria are in the water, they may make you sick if swallowed. There were 18 such outbreaks in 1998, in which thousands of people came down with stomachaches, nausea, and severe diarrhea (symptoms may take up to one week to appear). That year, a two-year-old died from an E. coli infection she contracted at a water park near Atlanta.

The key to safe swimming?Don't swallow. Don't even get water in your mouth. "The more water you drink, the more likely it is that you'll contract something," says Dr. Michael Beach, an epidemiologist with the CDC. He notes that the most common infections are from the parasites Giardia and Cryptosporidium, which survive the wrath of chlorine, and occasionally from E. coli, which can thrive when chlorine levels drop too low. But don't swear off the supersonic log flume just yet—just be smart and shut your trap.