Formula intolerance, also called an adverse
reaction to formula, encompasses a wide variety of pathogenic mechanisms,
including allergy. The child described in the vignette has a history consistent
with formula intolerance due to milk protein allergy. The infant's symptoms of
rash, emesis, and irritability are
consistent with an immunoglobulin E (IgE)-mediated reaction. Children, as young
as newborns, can have a milk protein allergy.
Milk protein allergy is one of many forms of formula intolerance. Other symptoms of formula intolerance can include diarrhea, constipation, bloody stools, or colic. Anaphylaxis is the most life- threatening symptom. The reaction experienced by the child in the vignette is not lactose intolerance, which can cause irritability but would not cause emesis or a rash.
A type II immunologic reaction is an antibody-antigen reaction. A good example is Rh incompatibility. These reactions are not IgE-mediated; they are mediated by IgG binding to a protein. In Rh incompatibility, the maternal IgG binds to the Rh protein on the infant's red blood cells. IgG reactions do not cause the symptoms seen in the child described in the vignette.
A type III immunologic reaction involves binding of IgG antibodies to an antigen, which triggers the complement cascade. An example of this type of reaction is serum sickness. Symptoms of this type of reaction are fever, joint pain, and swollen glands.
A type IV immunologic reaction is best exemplified by tuberculosis purified protein derivative test. This delayed type hypersensitivity reaction is mediated by T cells, not antibodies, and usually occurs 48 to 72 hours after the exposure. It is not characterized by rash, emesis, and irritability.
The child in the vignette is experiencing an IgE-mediated type I reaction to milk antigen in which IgE attaches to mast cells that bind with the milk antigen. Subsequent degranulation of the mast cells causes the symptoms described.
Baltimore RS. Nosocomial infection in the newborn. In: McMillan JA,
DeAngelis CD, Feigin RD, Warshaw JB, eds. Oskiís Pediatrics.
Principles and Practice. 3rd ed. Philadelphia, Pa: Lippincott Williams
& Wilkins; 1999:454-458
Harris JS, Goldmann DA. Infections acquired in the nursery:
epidemiology and control. In: Remington JS, Klein JO, eds. Infectious
Diseases of the Fetus and Newborn Infant. 5th ed. Philadelphia, Pa: WB
Saunders Co; 2001:1371-1418