A flight passenger made an observation after setting off an alarm while going through airport security — which sparked a “sweaty” conversation online.

Posted in the “r/tsa” forum on Reddit, the message was bluntly titled, “My crotch got flagged twice, thoughts?”

“I flew for the first time in 15 years this week and both airports flagged my crotch at the arms-up scanner,” read the post.

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The user added, “I don’t care about the pat-down. They were polite and professional and it doesn’t bother me, but I’m wondering what did it.” 

Plenty of other people took to the comments section to speculate about what could have set off the alarm.

A flight passenger (not pictured) made an observation after setting off an alarm while going through airport security — which sparked a “sweaty” and viral conversation online. (AP File Photo)

“It can alarm on heavy sweat (experienced that once myself), which will probably be somewhat more common now that we’re in the summer months,” claimed one user.

Another user asked, “Were you sweating?” to which the passenger responded, “Probably a little. I’m terrified of flying, so I was nervous.”

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“Last time I flew out of my home airport of Tampa, I got searched, too,” said a different person on Reddit. “The guard said something unnerving like ‘swamp rot’ or ‘swamp crotch’ or something similarly embarrassing.”

Another user remarked, “I didn’t read all the comments, but this happens to me when I’m late for a flight because I’m sweaty.”

People online have discussed how sweating may be a culprit in setting off TSA security alarms. (iStock)

“If you [go] through the machine that makes you put your hands above your head, it senses moisture,” the same person added. 

“I’ve been stopped for additional screening twice.”

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“Could be: clothes (baggy etc.), sweat, position (not on footprints, too wide or too narrow), zipper, too many layers, reflective stuff, ghosts, etc.,” commented one user.

A spokesperson for the Transportation Security Administration (TSA) told Fox News Digital that sweat could play a role in setting off alarms.

The TSA says that a person’s sweat could set off security alarms during a screening. (Andrew Harnik/Getty Images)

“Added moisture from a person’s body can alter the density of clothing, so it is possible perspiration may cause our Advanced Imaging Technology (AIT) machines to alarm,” said the spokesperson.

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“If this occurs, the passenger may need to undergo additional screening, such as a pat-down in the area of the body where the AIT alarmed, to ensure there is no threat,” the spokesperson added.