TSA Body Scanners Are Flagging Sweaty Travelers - Here's Why

A woman flying for the first time in 15 years was flagged twice at TSA security during the same screening - both times in the same area. She had no metal, no devices, no hidden objects. Just sweat. She shared the story on Reddit, sparking a wave of similar accounts from other fliers, according to Vice. The phenomenon, colloquially called “swamp crotch,” is an increasingly documented cause of false positives at TSA millimeter wave scanners.

Why It Happens

TSA millimeter wave scanners detect anything that interferes with the signal - including moisture. TSA expert Shawna Malvini Redden confirmed that perspiration is one of the stranger causes of false positives: the technology reacts to the way waves reflect off water. Professor Franklin Joseph, head of Dr. Frank’s Clinic, explained to The Sun that the groin area has a high density of sweat glands and is among the first areas to become damp in warm conditions, under tight clothes, or during anxious or rushed travel.

Beyond sweat, other triggers include feminine hygiene products, compression garments, and body shape. TSA states its equipment is designed to screen all body types effectively. France and Germany have both reportedly discontinued millimeter wave scanners due to high false-positive rates; in the U.S. they remain standard.

What Travelers Can Do

Experts suggest: wearing moisture-wicking underwear; applying anti-chafing powder before travel; choosing breathable cotton layers; and changing out of damp clothes promptly. General practitioner Dr. Claire Merrifield recommends washing the groin and underarm areas regularly, using fragrance-free products, and changing clothes frequently during warm-weather travel. Travelers flagged at the scanner can expect a same-sex pat-down of the flagged area; agents are trained to conduct these professionally.

References: People With Swamp Crotch Keep Setting Off TSA Alarms | Passenger Flagged by TSA After ‘Swamp Crotch’ Sets Off Alarm - and It’s Happening to Others, Too | ‘Swamp Crotch’ Is Setting Off Airport Security Scanners as GP Reveals Who’s at Risk and How to Avoid the ‘Embarrassment’