Mayonnaise is a thick, creamy dressing made from egg yolks, oil, a small amount of lemon juice or vinegar, and seasonings. It is used as a spread for sandwiches, a sauce for cold meats and fish, and as the basis for dips and salads dressings. Classic mayonnaise is not a cooked dressing but rather an emulsion. Egg yolks act as the emulsifying agent, keeping the oil and acidic ingredients from separating. Almost all mayonnaise is commercially produced. Homemade mayonnaise should not be made from raw eggs as it once was, but rather from cooked or pasteurized eggs.