Let’s first get a technical understanding of a desiccant. It is a hygroscopic substance that induces or sustains a state of dryness in its local vicinity in a moderately well sealed container. In other words a desiccant keeps what is inside your packaging dry. This is a great tool for a variety of consumer products. A common desiccant is silica gel. The solid beads are packed in permeable bags and are very effective at humidity control in packaging. Next is bentonite clay which offers better absorbency than silica gel in the average packaging environment. Production of bentonite desiccants has less impact on the environment and is usually less costly than silica gel. Other popular desiccants include activated carbon and molecular sieves. 

(Source: sud-chemie.com)