The complex process of digestion affects the timing, location, and particular symptoms of an allergic reaction to food. All of the symptoms of food allergy occur within a few minutes to an hour of eating. A food allergy can initially be experienced as an itching in the mouth and difficulty swallowing and breathing.

Then, during digestion of the food in the stomach and intestines, symptoms such as nausea, vomiting, diarrhea, and abdominal pain can start. Incidentally, the gastrointestinal symptoms of food allergy are those that are most often confused with the symptoms of different types of food intolerance.

As mentioned previously, the allergens are absorbed and enter the bloodstream. When they reach the skin, allergens can induce hives or eczema, and when they reach the airways, they can cause asthma. As the allergens travel through the blood vessels, they can cause lightheadedness, weakness, and anaphylaxis, which is a sudden drop in blood pressure. Anaphylactic reactions are severe even when they start off with mild symptoms, such as a tingling in the mouth and throat or discomfort in the abdomen. They can be fatal if not treated quickly.

Do Infants and Children Have Problems With Food Allergy?

Most allergies to foods begin in the first or second year of life. While some of these reactions may resolve over time (such as allergies to cow’s milk or eggs), other food allergies acquired in infancy (such as allergies to nuts or shellfish) typically persist throughout life. Allergies to milk or soy formula (a milk substitute made from soybeans) sometimes occur in infants and young children. These early allergies sometimes do not involve the usual hives or asthma but rather can cause symptoms resembling infantile colic, and perhaps blood in the stool, or poor growth.

The clinical picture of infantile colic, which usually starts within one month of birth, is that of a crying child who sleeps poorly at night. The cause of colic is uncertain. A variety of psychosocial and dietary factors have been implicated, however, and allergy to milk or soy has been proposed as a cause of colic in a minority of infants with colic.

In infants, food allergy is usually diagnosed by observing the effect of changing the infant’s diet; rarely, by using a food challenge. If the baby is on cow’s milk, the doctor will suggest a change to soy formula or breast milk only, if possible. If the soy causes an allergic reaction, the baby can be placed on an elemental formula. These formulas are processed proteins and carbohydrates, basically amino acids and sugars, and contain few, if any, allergens.

Breastfeeding:

Exclusive breastfeeding, that is, excluding all other foods, for at least the first four months of life appears to help protect high-risk children against milk allergy and eczema in the first two years of life. Breast milk contains less protein that is foreign to the infant and, therefore, is less allergenic than cow’s milk or soy formula. Exclusive breastfeeding should be a consideration, therefore, especially in infants who are predisposed to food allergy. Some children are so sensitive to a certain food, however, that if the mother eats that food, sufficient quantities enter the breast milk to cause a reaction to the food in the child. In this situation, the mothers themselves must avoid eating those foods to which the baby is allergic. No conclusive evidence has been obtained that suggests that breastfeeding prevents the development of allergies later in life.

Special considerations in children:

An allergic child who itches, sneezes, and wheezes a lot can feel miserable and, therefore, sometimes misbehave or appear hyperactive. At the other extreme, children who are on antiallergy medicines that can cause drowsiness may become sleepy in school or at home. Parents and caregivers must understand these different behaviors, protect the children from the foods that induce their allergies and know how to manage an allergic reaction, including how to administer epinephrine. Also, schools need to have plans in place to address emergencies, including anaphylactic shock.