Safety threats presented by the potential use of common items to cause harm during air travel have caused the U.S. Department of Homeland Security and the Transportation Security Administration to publish a list of Prohibited Items for Air Travel.
That list was updated in August 2006 to include liquids and gels, which now must be carried on in three-ounce or smaller containers. These containers must be placed in a single, quart-sized, zip-top, clear plastic bag. Larger items should be placed in checked baggage. This includes shampoo, sun tan lotion, creams, toothpaste, hair gel and other items of similar consistency. Exceptions include baby formula and medication, which must be presented for inspection at the checkpoint.
Also, beverages purchased in the boarding area, beyond the checkpoint, will not be permitted onboard aircraft.