This is why airport body scanners sometimes flag random items on you

A regular part of traveling these days is going through an airport body scanner before boarding a plane. Even if you follow protocol and take everything out of your pocket, you may still get flagged. Maybe this makes you wonder: What exactly do airport body scanners detect? This is actually a very common question asked online, with travelers mentioning that everything from sweaty armpits to small skin lesions get flagged. Most people I know have fired up a scanner at one point or another, which usually results in a few extra taps on areas of the body the scanner deems suspicious. Nine times out of ten, people are sent away quickly.

However, a case study published in JAMA Dermatology found that new airport body scanners that use radio frequencies may flag things on travelers' bodies that are not actually security threats. Airport body scanners are designed to detect lumps on your body or hidden inside clothing - however, in rare cases, a protrusion on your body may trigger the scanner. "Airport scanning equipment detected a 1.5 cm epidermal inclusion cyst in an airport traveler, prompting security personnel to conduct an invasive security search for hidden explosives," the study said. "The traveler was subsequently provided with a medical explanation letter to show to airport security on future journeys.”

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For people with health conditions, sexual assault survivors, and people with anxiety, undergoing further pat-downs can be very frustrating, to say the least. According to the National Network on Rape, Abuse & Incest, if you are a sexual assault survivor, you can request a private exam and even request a specialist in advance.

Generally speaking, body scanners are designed to detect non-metallic items on the human body that metal detectors might miss, USA Today reported. The scanner cannot see the inside of your body, and you will not appear naked during the scan. If you do fire up the scanner and there's nothing on you, you'll most likely be fine. USA Today notes, "Since May 2013, the full-body scanners used at all airports are known as 'millimeter wave' machines, which bounce electromagnetic waves off travelers to provide animated images of possible suspicious items."

Things like having your socks bunched up, extensions or bobby pins in your hair can get you marked. Once TSA determines why the scanner was triggered, you're usually good to go. I've tripped over the scanner six times with my hair, but once they felt my head, they let me go. Underwire bras can also get you flagged when going through a body scanner or metal detector, according to the Scan-X Security website. If you want to avoid extra flapping, don't wear anything in your hair and opt for a wire-free bra.

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Overall, your best bet for getting through a body scanner quickly is to dress simply and remove everything from your pockets, including small pieces of paper. If you have body piercings, they may trigger the scanner, but travelers on forums with body piercings also report no issues getting through airport security. I've had a few body piercings and they've never set off any metal detectors or scanners.

If you do get reported, you will be sent away once it is determined you were wearing body jewelry. If full-body scanners creep you out, you can opt out entirely and request a pat-down by a TSA officer of your own gender, though this usually takes longer, so be sure to allow extra time at the airport. Let’s face it—just about everything in the airport is a huge pain in the ass these days, but knowing what to expect in advance can help make the experience less terrible.