[Robyn O'Brien's] story is one of several in a new book, Healthy Child, Healthy World. About two years ago, she fed her youngest child scrambled eggs. The baby's face quickly swelled into a grotesque mask. Little Tory had a severe food allergy, and Ms. O'Brien's journey had begun. Her theory - that the food supply is being manipulated with additives, genetic modification, hormones and herbicides, causing increases in allergies, autism and other disorders in children - is not supported by leading researchers or the largest allergy advocacy groups. [But] record numbers of parents are heading to doctors concerned that their children are allergic to a long list of foods. States are passing laws requiring schools to have policies protecting children with food allergies. No one knows why the number of allergies seems to be on the rise. Ms. O'Brien and leading allergy researchers agree that few reliable studies on food allergies exist. The best estimates suggest that 4 to 8 percent of young children suffer from them. Many health professionals, though, agree that something is changing. The hygiene hypothesis intrigues many researchers. It holds that children are being exposed to fewer micro-organisms and, as a result, have weaker immune systems. "But this alone cannot account for the massive relative increase in food allergy compared with other allergic disease such as asthma," said Dr. Marc E. Rothenberg, the director of allergy and immunology at Cincinnati Children's Hospital Medical Center. [Ms. O'Brien] chides top allergy doctors who are connected to Monsanto, the producer of herbicides and genetically modified seeds. She asserts that the Food Allergy and Anaphylaxis Network, the nation's leading food allergy advocacy group, is tainted by the money it receives from food manufacturers and peanut growers.