Cow milk allergy is the most common food allergy in childhood, it occurs in about 2 to 3% infants in the first year of life. Most infants with cow milk allergy develop symptoms before 1 month of age, often within 1 week after introduction of cow milk protein-based formula.

Symptoms suggestive of cow milk allergy may be encountered in approximately 5 to 15% of infants. The majority of children with cow milk allergy 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 cow milk intake (immediate reactions) or after 1 hour (late reactions).

Likely, the overall outcome of cow milk allergy in infancy is good, with a global remission rate of approximately 85 to 90%. In particular, cow milk allergy tends to resolve in approximately 45 to 50% of children at 1 year, 60 to 75% at 2 years, and 85 to 90% at 3 years.

Associated allergic reactions to other foods, as egg, fish, cereals, nuts and soybean, develop in up to 50% of children and allergy against inhalants shows up in 50 to 80% before puberty. The food allergy prevalence is greatest in the first year of life, affecting 6% to 8% of infants. Even exclusively breast fed infants may react against food proteins transferred from the mother’s diet into her breast milk: the incidence of confirmed cases is almost 0,5%.