A review of the common sources of aluminum for humans found that antiperspirant use can significantly increase the amount of aluminum absorbed by the body. According to the review, after a single underarm application of antiperspirant, about .012 percent of the aluminum may be absorbed.
Other concerning sources of aluminum to humans are food, drinking water, contaminated air, and industrial and medicinal, such as vaccines, exposure.
Pharmacological Toxicology April, 2001;88(4):159-67