Despite widespread concern over a possibility that genetically engineered crops could cause human health problems, there has been little evidence that this has occurred. But in a move that could have severe ramifications for the biotech industry, the US Food and Drug Administration (FDA) is investigating several cases of allergic reactions to StarLink corn in humans.

The health complaints about the biotech corn are the first lodged by consumers against an engineered food. The cases emerged after several people reported reactions to tacos shells and most recently in corn dogs.

The genetically modified corn had only been approved for animal consumption because of concerns it might trigger dangerous allergic reactions in people, but the corn was inadvertently mixed with corn destined for the human food supply. At that time federal and industry officials emphasized that no significant health hazard was involved to humans from the corn.

Aventis CropScience,which markets the corn, argues that that StarLink could not cause severe, or even minor, allergic reactions, and that the corn is safe. The company says that the quantities of StarLink in processed food are too small to cause allergic reactions and that its research showed that the Cry9C protein was destroyed during the production process for food such as tacos. The company has been pushing for its approval for human use despite recalls of food containing the StarLink corn last year.

The FDA is currently testing blood samples from people who have suffered an allergic reaction to the corn, but researchers have warned that the test will not give a definitive answer. If the test is negative it will provide a boost to the biotech industry as it may prove that genetically engineered food is safe to eat.

Karl Klontz, a medical officer with the FDA's Center for Food Safety and Applied Nutrition, said the test would determine whether the people had produced antibodies to the genetically modified protein in StarLink corn, called Cry9C, which protects plants against the European corn borer.

"The presence of the antibody would suggest the possibility of an allergic phenomenon, and the lack of the antibody would go a long way to reassure that there is no allergic issue," said Klontz.