Insects," says Sarah-Lou Reekie, "are known to like excited, emotional blood." No wonder, then, that when Anna and the King began filming in Malaysia last winter, the cast and crew—you know, dramatic showbiz types—became popular with the local hexapods. Luckily, Reekie was able to save their skin. After getting a call from an assistant on the movie, which stars Jodie Foster, Reekie shipped off a crate of Alfresco, the plant-based, chemical-free insect repellent she developed and sells by mail order ($25 for a 6.8-oz. bottle). "We have every kind of bug on the planet," says Morag Ross, Anna's makeup designer, "and I don't have one bite."

Stories like that don't surprise Reekie, 48, whose potion also came to the rescue on the Montana set of Robert Redford's The Horse Whisperer. "Alfresco's ingredients [Melissa, lavender and geranium] are known to be anti-insect," she says. "They also make you feel relaxed so the body gives off signals that are unattractive to insects."

The daughter of a London interior designer, Reekie "wasn't interested in plants," she says, until she and her husband, Charles, 47, a business consultant, bought a house with a garden in London in 1991. Suddenly fascinated, she began volunteering at London's Chelsea Physic Garden, a botanical enclave—and getting bitten. Because repellents irritated her skin, she worked with a biochemist and started experimenting. "I put lotion on the ground to see if ants went away from it," says Reekie. When they did, she knew she had her formula (the London School of Hygiene & Tropical Medicine, which put Robert Redford in touch with Reekie in 1997, confirmed her results).

Today, Reekie has five employees, and orders average 150 bottles a week. Ingredients are so costly that she has yet to turn a profit. But, as Reekie quipped to Britain's Daily Telegraph, if Hollywood stays interested, "I should get an Oscar."