After drycleaning or laundering, and oil stain can form small crosses as it spreads in the direction of individual yarns. On knit fabrics, such stains can result in sharp leave-off streaks. The stains can be yellow, tan or rust in color due to contact with cooking oils, mayonnaise, medicinal oils, lubricants, skin lotions, and salves. Such stains are often invisible until atmospheric exposure causes discoloration over time. Heat used during drying or finishing after cleaning can accelerate this oxidation process. If the stain is fresh, professional oil removing treatments are satisfactory. Once the stain oxidizes, it becomes much more difficult to remove, although professional cleaners can sometimes reduce the visibility of the stain.