dairyless

As a noun lactose

is the disaccharide sugar of milk and dairy products, C₁₂H₂₂O₁₁, (a product of glucose and galactose) used as a food and in medicinal compounds.

As an adjective dairyless is

without dairy ingredients; lactose-free.

As adjectives the difference between dairy and dairyless

is that dairy is referring to products produced from milk while dairyless is ( offood) without dairy ingredients; lactose-free.

As a noun dairy

is a place, often on a farm, where milk is processed and turned into products such as butter and cheese.