Immunoassays are analytical techniques based on the recognition between an antigen and an antibody. These techniques are highly specific and sensitive and allow the direct detection and/or quantification of traces of analyte in a complex medium (food matrix) often without requiring extraction of the compound. Most of them are fast allowing the analysis of a sample within a few minutes. The main antigens are proteins and polysaccharides; however, immunogenicity of small molecules such as chemical contaminants can be achieved by coupling them to a carrier protein. Among the different immunochemical techniques available, ELISAs are the most widespread, whereas immunosensors are getting more and more popular. In milk and dairy products, immunochemical techniques have been applied to the detection and/or quantification of proteins (enzymes, allergens, hormones …) chemical contaminants, drug residues and antibiotics, toxins and pathogens. They have also been widely used for detecting milk adulteration (detection of cow's milk into ewe's or goat's milk and vice versa).