The reason you always get swabbed at the airport is to check for any potential explosives like explosive powder residue on your hands or body.
While it's generally luggage that is subject to swabbing, travelers clothes and hands may also be swabbed.
Swabbing is used as a secondary form of detecting explosives alongside full-body scanners.
While the process can be a little intimidating, a positive swab test is no need to panic.
American Airports are so strict as a result of the 9/11 attacks on New York which happened on September 11th 2001.
On September 11th 2001 4 airplanes were hijacked and flown into the world trade centers in New York killing all the passengers and crew and the hijackers on board the airplanes and several people inside the world trade center buildings.
Security at airports was really ramped up and increased since the September 11th attacks to hopefully prevent any more attacks and hijacks of the planes.
"The goal of aviation security is to prevent harm to aircraft, passengers, and crew, as well as support national security and counter-terrorism policy."
Airports have to be diligent against all forms of terrorism, both foreign and domestic.
There have been incidents of American citizens hijacking aircraft.
On September 11, 2001, terrorists hijacked four commercial airplanes, using them as weapons in a coordinated attack against the United States.