Giving foods like nuts, dairy products and fish to young children is also controversial.
"We don't understand food allergies as well as we understand inhalation allergies," Bonagura said.
Many children, according to Bonagura, grow out of an allergic response to milk or eggs by age 5. Peanut and shellfish are more problematic, however, and can cause lifelong allergies.
Peanuts and milk are commonly associated with childhood allergies, but boiling these foods may remove their allergic potential. A recent study finds that boiled peanuts don't cause the allergic response that is caused by dry-roasted peanuts -- the type found in peanut butter.
Medical researchers now believe immunoglobulin E (Ig E), the immune system antibody that causes the body's response to allergens, may not recognize the proteins in peanuts or milk after the foods are boiled.
"If you can denature [damage] the protein that causes the Ig E response, it's unlikely to trigger an allergic response," Bonagura said.
Even with all the debate about preventing childhood allergies, some consensus emerges that can give parents the advice they're looking for to keep their kids healthy and safe. Nelson and other experts point to the recommendations provided by the American Academy of Allergy, Asthma and Immunology for introducing new food to your child.
Solid food, including fruit, vegetables and meat, should be introduced only after six months. After a year, dairy products like milk, yogurt and cheese can be given. Eggs, according to the academy, may be safely given to the child after two years, but nuts and fish should be given only after the child is at least 3 years old.
There is one allergy-causing factor that causes no dissent among experts: smoking.
"The one that nobody questions is exposure to passive smoking, both in-utero [from the mother smoking] and after birth," Nelson said.
"You certainly need to add tobacco smoke as a pollutant contributing to asthma," said William Fisk, senior scientist and head of the Indoor Environment Department at Lawrence Berkeley Laboratories in Livermore, Calif. "It's a very important pollutant, and it has been linked to a number of health effects."
Besides avoiding smoking around children, Fisk has additional advice for parents. Leaving pets outdoors and fixing water leaks will help alleviate pet dander and mold. Keeping a home free of cockroaches and rodents is also important, though this may be difficult in poor, inner-city neighborhoods.
"Technically, there's a lot we can do here, but socially there's not a lot we can do, especially when there's poverty present," Fisk said.