The Threat: Picnics mean deviled eggs and macaroni and potato salad. But allowing these cookout staples to stay out too long could leave your guests with a nasty stomach bug.
"The two main problems of foodborne illness in the U.S." says Williamson, "are not cooking food to a high-enough temperature, and leaving food out at an unsafe temperature." Don't leave any food items out for longer than two hours, she adds, and in very hot, 90-degree-plus temperatures, take it inside after an hour.
The Fix: Scrub fruits and veggies used in salads thoroughly before cutting. Keep deviled eggs and salads cold—packed in a cooler that's filled 75 percent with food and 25 percent with ice or frozen drinks or cold packs, to allow cold air to circulate freely. Cold food should be kept at 40° F or below.
More: Food Poisoning or Flu? How to Tell the Difference