Miami ? When Luckner Pierrsaint feels congested from the flu or bronchitis, he doesn’t go to a doctor or a drugstore. He takes his own concoction: a spoonful of a sugar-and-purple-onion mixture left outside for three nights.

Pierrsaint fled Haiti for Florida in 1989 but still relies on the plant-based remedies he learned back home from his father and grandfather, both voodoo priests.

“In my country, it can take three days to see a doctor, so we know what to do,” said Pierrsaint, 52, who grows ingredients in his North Miami backyard.

Faced with skyrocketing health care costs, lack of insurance and language barriers, many immigrants believe they are better off with homegrown remedies from their native lands than conventional treatments.

Doctors once dismissed alternative therapies because there is no scientific proof the remedies work, but the treatments are beginning to win some mainstream acceptance.

More than a third of American adults have tried alternative medical therapies, including prayer, folk medicine and natural products, according to a 2002 survey by the National Center for Complementary and Alternative Medicine, part of the National Institutes of Health.

But the Food and Drug Administration cautions that “natural” doesn’t necessarily mean safe because alternative medicines do not undergo the rigorous testing required for conventional medicines. There are no scientific studies to determine the correct dosage, side effects, or risk of interactions with other medication or certain foods.

In 2003, for example, the FDA warned against drinking teas brewed from star anise plants, believed to soothe colic in infants. That is because the Chinese star anise is often indistinguishable from a toxic Japanese star anise plant, which can cause serious neurological problems such as seizures.

Dr. Marie-Denise Gervais, who practices at a free clinic in Miami’s Little Haiti neighborhood, has seen poor patients jeopardize themselves by relying on alternative therapies, such as a woman with high blood-sugar who was at risk for a diabetic coma.

She had difficulty buying insulin but paid $50 for a homegrown remedy.

“God knows if this potion is loaded with sugar,” Gervais said.

Nearly half of foreign-born non-citizens in the United States lacked health coverage in 2003, according to a recent study by the Employee Benefit Research Institute. The nonpartisan research group blamed the problem in part on a 1996 federal law banning legal immigrants from participating in public insurance programs for five years after arriving in this country.

Patients add to the treatment risks when they finally see doctors but fail to tell them about home remedies they have used.