Since the 1930's the scientific literature on cow's milk protein allergy (CMPA) has accumulated. Over the last decade new diagnostic tools and treatment approaches have been developed. The diagnosis of reproducible adverse reactions to cow's milk proteins (CMP), i.e. CMPA, still has to be confirmed by controlled elimination and challenge procedures. Advanced diagnostic testing using epitope and microarray technology may in the future improve the diagnostic accuracy of CMPA by determination of specific IgE against specific allergen components of cow's milk protein. The incidence of CMPA in early childhood is approximately 2-3% in developed countries. Symptoms suggestive of CMPA may be encountered in 5-15% of infants emphasizing the importance of controlled elimination/milk challenge procedures. Reproducible clinical reactions to CMP in human milk have been reported in 0.5% of breastfed infants. Most infants with CMPA develop symptoms before 1 month of age, often within 1 week after inter introduction of CMP-based formula. The majority has two or more symptoms from two or more organ systems. Approximately 50-70% have cutaneous symptoms, 50-60% gastrointestinal symptoms and 20-30% 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%. The basic treatment of CMPA is avoidance of CMP. In early childhood a milk substitute is needed. Documented extensively hydrolysed formulas are recommended, whereas partially hydrolysed formulas should not be used because of a high degree of antigenicity and allergenicity associated with adverse reactions. In case of intolerance to extensively hydrolysed formulas and multiple food allergies a formula based on aminoacids is recommended. Alternative milk substitutes such as sheep's and goat's milk should not be used because of a high degree of cross reactivity with CMP. Milk from other mammals such as mare and donkey may be tolerated by some children with CMPA. Soy protein is as allergenic as CMP and soy formula is not recommended for young children with CMPA because of a great risk of development of allergy to soy, whereas soymilk is normally tolerated in older children with CMPA. Recent treatment modalities are oral immunotherapy (OIT) involving the ingestion of increasing amounts of milk allergen on a regular basis to desensitize and potentially permanently tolerize patients to CMP. OIT can increase the reaction thresholds to CMP, but questions about safety and long-term efficacy remain. Anti-IgE therapy with Omalizumab may improve the safety and efficacy of OIT and may provide benefit in monotherapy.