The swelling and bioadhesion of hydrogels can be controlled based on the fluid environment they are introduced to in the body. These properties make them excellent for use as controlled drug delivery devices. Where the hydrogel adheres in the body will be determined by its chemistry and reactions with the surrounding tissues. If introduced by mouth, the hydrogel could adhere to anywhere in the gastrointestinal tract including the mouth, the stomach, the small intestine, or the colon. Adhesion in a specifically targeted region will cause for a localized drug delivery and an increased concentration of the drug taken up by the tissues.