Lactose

Lactose is the name for the type of sugar that’s found in milk.  Brewers use lactose to add sweetness and a thicker mouthfeel to beers because it’s a sugar that brewing yeast can’t ferment. Lactose is primarily used in stouts, where the sweeter flavor profile can complement the malt and chocolate notes, but in the last several years it’s been added to other styles of beer too. For example, Juicy/Hazy IPAs sometimes include lactose as a means to give the flavor profiles a fruit juice or milkshake quality.