Defoaming agents are added to prevent or counter the foam generation in the formulation. Generally, these agents have surface active properties and are insoluble in the foaming medium. These are less viscous, easily spreadable on the foamy surface, and possess an affinity to the air–liquid surface where it destabilizes the foam lamellas, which rupture the air bubbles and break down the surface foam. Entrained air bubbles are agglomerated, and the larger bubbles rise to the surface of the bulk liquid more quickly.

Commonly used defoaming agents are certain alcohols (cetostearyl alcohol), insoluble oils (castor oil), stearates, polydimethylsiloxanes and other silicones derivatives, ether and glycols .