Allergic reactions can occur immediately, or they can be delayed and take days to surface. A delayed allergic reaction can make it more difficult to pinpoint the allergen.

Common symptoms of an allergic reaction are respiratory congestion, eye inflammation, swelling, itching, hives, and stomachache and vomiting. Food allergies can contribute to chronic health problems, such as acne, asthma, bedwetting, diarrhea, ear infections, eczema, fatigue, hay fever, headache, irritability, chronic runny nose, and even difficulty maintaining concentration (attention deficit disorder, or hyperactivity). Food allergies can also cause intestinal irritation and swelling that interferes with the absorption of vitamins and minerals. Even if you are providing your child with a wholesome, nutritious diet, if she is consuming foods to which she is allergic, she may not be able to absorb food properly, and therefore may not be deriving the full benefits of all the foods she is eating.

The most common foods that cause allergic reactions in children are wheat, milk and other dairy products, eggs, fish and seafood, chocolate, citrus fruits, soy products, corn, nuts, and berries. Many children also are allergic to sulfites, which are found in some frozen foods and dried fruits, as well as in medications. Some people seem to be genetically predisposed to food allergies. If family members, especially parents, have food allergies, there is a greater chance a child will have the same difficulties.

Sometimes, if all the irritating foods are eliminated from a child's diet for several months, her body will have a chance to rest and heal, after which it will be able to handle small amounts of these foods without reacting. Sometimes, too, there is an underlying issue such as a parasitic or yeast infection in the intestine that is contributing to the allergic response. If these underlying problems are cleared up, the child's body may be less reactive to certain substances.

It has been observed that some children actively dislike the foods that produce an allergic reaction. They seem to know instinctively that certain foods will cause a problem. If your child continually refuses particular foods, it may be wise not to force the issue.

Paradoxically, however, some children seem to be particularly drawn to the very foods that cause a problem. For example, many children are allergic to peanut butter, a staple in many homes. Children who continually ask for peanut butter, or those who enthusiastically eat lots of wheat bread, wheat crackers, and wheat cereals, or who crave milk, ice cream, and other dairy products, may actually be exhibiting an allergy to those foods.