The onset and exacerbation of food allergies in children has recently been increasing. To investigate the correlation between the development of milk allergies and epicutaneous sensitization with milk allergens, we determined the amount of milk allergens in cosmetics and quasi-drugs used for skin care. The amount of αS1-casein and β-lactoglobulin was determined in 29 products using immunochromatography and enzyme-linked immunosorbent assay. In 9 of the 29 products, the levels of αS1-casein and β-lactoglobulin were quantified in the range of 7.1-18,810μg/g and more than the limit of detection (LOD) to 10,429μg/g, respectively. Both αS1-casein (7.1-18,810μg/g) and β-lactoglobulin (4.4-10,429μg/g) were detected in 5 products that displayed unfractionated milk ingredients such as yogurt or dried nonfat milk on the labels. On the other hand, β-lactoglobulin was detected in only 2 of 15 products (6.6μg/g and 6.9μg/g) that displayed whey fraction on the label. In addition, the amount of αS1-casein was less than LOD in 23 products that displayed whey, casein, or nonprotein fraction on the labels. According to these results, the levels of αS1-casein and β-lactoglobulin tend to be influenced by the forms of milk ingredients. Thus, these analyses revealed that 31% of randomly selected products contained detectable levels of αS1-casein and β-lactoglobulin. Moreover, 4 of the 9 allergen-positive products, including soap, lotion, and bath powder, were recommended for infant use. Our study provides the first data regarding cosmetics containing allergens and the development of food allergy. These results suggest that the continuous use of cosmetics containing milk allergens may induce epicutaneous sensitization with milk allergens.