Frequency of cow's milk allergy in childhood

Objective: The primary objective of this review is to discuss the clinical features, diagnosis, natural history, and prognosis of cow's milk allergy in early childhood and its relationship to development of inhalant allergies. Data Sources: A review of 229 PubMed (National Library of Medicine) articles on cow's milk allergy (CMPA) for the years 1967 through 2001 was performed. In addition, references from other review articles have been included. This review represents a synthesis of these sources and the expert opinion of the author. Study Selection: The expert opinion of the author was used to select the relevant data for this review. Results: The diagnosis of reproducible adverse reactions to cow's milk protein (CMP), ie, CMPA, has to be confirmed by controlled elimination and challenge procedures. The incidence of CMPA in infancy seems to be approximately 2 to 3% in developed countries. Symptoms suggestive of CMPA may be encountered in approximately 5 to 15% of infants emphasizing the importance of controlled elimination/milk challenge procedures. Reproducible clinical reactions to CMP in human milk have been reported in approximately 0.5% of breastfed infants. Most infants with CMPA develop symptoms before 1 month of age, often within 1 week after introduction of CMP-based formula. The majority has two or more symptoms from two or more organ systems. Approximately 50 to 60% have cutaneous symptoms, 50 to 60% have gastrointestinal symptoms, and approximately 20 to 30% respiratory symptoms. Symptoms may occur within 1 hour after milk intake (immediate reactions) or after 1 hour (late reactions). The prognosis of CMPA is good with a remission rate of approximately 45 to 50% at 1 year, 60 to 75% at 2 years, and 85 to 90% at 3 years. Associated adverse reactions to other foods develop in up to 50% and allergy against inhalants in 50 to 80% before puberty. Conclusions: CMPA is the most common food allergy in early childhood with an incidence of 2 to 3% in the first year of life. The overall prognosis of CMPA in infancy is good with a remission rate of approximately 85 to 90%. In particular, gastrointestinal symptoms show a good prognosis. An early increased immunoglobulin E-response to CMP is associated with an increased risk of persistent allergy to CMP, development of adverse reactions to other foods, and development of asthma and rhinoconjunctivitis later in childhood.