Mayonnaise is made from eggs, oil and lemon juice and is not considered a dairy product. Eggs, which come from a chicken do not contain lactose like dairy products, which come from cow, goat or sheep milk.
The confusion over whether eggs are a dairy product is derived from a misconception about the terms animal by-product and dairy product. Eggs are an animal by-product, but do not cause any problems when eaten by people suffering from an allergic reaction to lactose-containing products. For people who are unable to eat eggs for health or ethical reasons, there are many egg-free mayonnaise products available.