How To Help Avoid Getting A False Positive On TSA Swab Tests

by SharonKurheg

If you’re traveling by plane in the United States, you know that sometimes you’ll get pulled aside for a “swab test.” It happened to me on our way home from New Orleans not long ago. I had nothing to hide and we were way early for our flight at MSY, so I stayed good-natured and joked with the TSA officer that if he opened my carry on bag, he was going to have to close it too, cuz it was stuffed to the gills and had taken me 10 minutes to get the zippers to close ;-). He didn’t share my good humor, but he did re-zipper the bag.

Being a “chosen one” appears to be random (although some think it’s if you look suspicious or if a TSA officer still has to fill their quota for the day) and it’s certainly harmless enough – they swab your hands (and/or your laptop, shoes, film, cell phone, bags, wheelchair or cast) with a cotton cloth and check for explosive residue in an Explosives Trace Detector (ETD).



If you test negative, you’re free to go. But if you’re positive, you have to go to the next step of security.

The problem is that some people wind up with a false positive. Here’s why:

See, the test is looking for the stuff bombs are made of and the two chemical compounds that are usually used are nitrates and glycerin.  The thing is, there are a lot of typical, everyday things that have those chemicals in them:

  • hand soaps that contain glycerin
  • lotions that contain glycerin
  • cosmetics, hair products, etc. which may contain glycerin
  • baby wipes that may contain glycerin
  • certain medications (e.g., nitroglycerin and other nitrates)
  • lawn fertilizers
  • munitions
  • accelerants
  • fireworks and other pyrotechnics

So what can you do? Simple. Before you get to X-ray, wash your hands…REALLY well (don’t forget to scrub your cuticles and under your fingernails!). Make sure there are no remnants of soap or lotion (or meds or munitions or fireworks) on them. If you recently used a baby wipe, again, make sure your hands have been washed afterward (although really, if you’re using a baby wipe for its intended use, I hope you’re washing your hands anyway, if you catch my drift). Same thing with your shoes, and if your suitcase or laptop or anything else may have somehow come in contact with any of those chemicals, wipe them down too.

If you still get flagged as positive, don’t make a fuss – most likely you’re going to get patted down again by a TSA worker of the same gender as you (Can you refuse a TSA pat down? Here’s what we found out). If you become belligerent or hostile, they’re just going to think you have something to hide and it certainly won’t get you through the process any faster. So let them do their job and if you have nothing to hide, you should be done soon enough anyway. Assuming you got to the airport far enough in advance (here’s how to figure out how early you should arrive at the airport), the chances of you missing your plane because of this short delay are pretty small.

By the way, if you’re aware of any contact you may have had with those chemicals, let the TSA workers know…it might help them get to the bottom of things faster so you can be on your merry way.

By the way, you can probably thank, in part, the would-be bomber of the Dec. 25, 2009 Northwest Airlines flight 253 over Detroit for prompting the whole hand-swabbing thing. The year after that, TSA implemented the program and spent about $60 million on ETD machines. They’ll never admit that’s why the hand swabbing all started but really, c’mon, what else could it be? So thanks, bomb failure dude!

As for my recent encounter with the TSA officer in New Orleans? He swabbed my 3 bags of PJ’s Coffee (I luuuuuuuv PJ’s Coffee – even more than Starbucks!) and nothing else in the suitcase. All negative. Yay!

A tip of the hat and a huge THANK-YOU to Shannon D., who gave us the initial heads up about this topic!

Feature Photo: TSA

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Kelly MacKay January 30, 2018 - 8:36 am

I haven’t flown to the US in many years but I have never heard nor experienced this TSA test, I ve walked through metal detectors, and had wand waved over me. I’ll have to look it up. Is this only done in the USA?

SharonKurheg January 30, 2018 - 9:41 am

Hi Kelly! I can’t speak for other countries (we travel quite a bit but only travel internationally once every other year or so) but the TSA has been doing it since at least 2010, if not before then. Not everyone get swabbed (unlike going through the metal detector, which just about everyone does, or the wand, which happens relatively frequently) and I think it’s only happened to me a small handful of times. So I could see how you might not have experienced it. 🙂

Kelly MacKay January 30, 2018 - 10:24 am


Tony October 18, 2020 - 10:53 pm

they’ve done this plenty of times to me in australia and sometimes hong kong. Its always random, which is why i think its silly. if you want to test someone for explosives, why leave it to random chance? And even if you test positive, theres so many plausible reasons that its a moot point if security doesn’t find anything on u.

Mfb123 April 29, 2019 - 2:39 pm

I’ve had two false positives…once on my shoes, once on my laptop. To this day, I have no idea what triggered it.

SharonKurheg April 29, 2019 - 10:40 pm

They swabbed my hands once. I’m guessing hand lotion? But I ddin’t know better then. I sure do now! 😉

V April 30, 2019 - 12:35 am

Thanks for giving the bad guys a heads up for getting away with anything bad planned😕

SharonKurheg April 30, 2019 - 12:43 am

I’m sure the bad guys already know. After all, all it takes is a simple Google search to find out that kind of info. The stuff TSA really doesn’t want us to know because it’s a sign of a security risk, we don’t know 😉

YULtide May 4, 2019 - 7:59 pm

I got a false positive once at LHR and after I had been cleared the agent told me that recently polished shoes can cause a false positive.

SharonKurheg May 4, 2019 - 9:08 pm

Wow, never heard of that one!

Glenda Collier August 27, 2019 - 12:34 am

I had a stopover in Iceland to return to the U.S. I was “randomly” chosen for security with an ssss written on my boarding pass. I’m 67 age, a past teacher, not criminal record. I received a swab “test” on my hands, my stomach and above my socks on both feet. I’ve felt sick ever since. What is the liquid the TSA puts on the cloth for the swab test. Bye the way, I use glycerine soap, that’s probably all it was. People in there with a baby, probably glycerin from the baby wipes, a young female college student. All of these terrorist looking people.

SharonKurheg August 27, 2019 - 12:52 am

You kind of lost me on your last sentence – “All of these terrorist looking people.” Anyone could potentially be a terrorist, regardless of what they look like, no?

drrichard April 17, 2023 - 7:17 am

Flying while Middle Eastern looking is a great way to be checked more often in Europe and North America.

CHRIS October 18, 2020 - 8:24 pm

You think TSA puts a liquid on the swabs to make people sick? What’s your opinion of the AIT?…..perhaps a mind-control device?

Jennifer K Lovett May 25, 2021 - 11:57 am

I have been stopped both times I was swabbed. I use wooden matches. Could that be my problem?? The person both times was really cranky about the whole thing. I did not have any problem, just wished I knew what I could have touched. She didnt care to tell me.

sunkissedpeach386 June 13, 2021 - 3:35 pm

My boyfriend just got flagged on a return trip – he had just used hand sanitizer (of which glycerin is a main ingredient along with alcohol). Why are they bothering to test for this now with COVID-19 and so many false positives?????

SharonKurheg June 13, 2021 - 3:43 pm

No idea. But I suspect because, despite all the false positives, they’ll also still occasionally find someone who has residue of bomb materials on their hands or possessions.

derek April 30, 2022 - 6:55 pm

Being patted down by a TSA employee of the same gender as a matter of policy is an attack on LGBTQIA2S rights. Use of the same gender assumes that homosexuals do not exist. This should stop. The gender of the TSA employee should be random. Instead, there could be video if the TSA employees are thought to be unprofessional.

SharonKurheg April 30, 2022 - 7:41 pm

I would hope that if the person being patted down is of the LGBTQ+ community, or is concerned that the person patting them down is, that they say something before said pat down.

JJ May 1, 2022 - 4:55 am

This is good timing. I’ve had this happen many times in the USA and always negative but this happened to me yesterday at MAD airport (fast lane) and it came back positive. I had to wait for the police to show up (5 mins) and they just took a picture of my boarding pass, passport, and asked me what I did for work and said ‘have a good flight”

JT May 1, 2022 - 9:59 pm

I hate these “swab” tests. We learned the hard way years ago at the Omaha airport when we were detained and almost didn’t make the flight due to the delays. The issue was that we had had massages right before going to the airport, then learning that most lotions contain nitroglycerin. We even got put in a “special room” while they figured out what to do with us. I think because we are white men is the only reason they ultimately let us go. I also recently had a false positive due to being flagged by having protein powder (sealed) in my carry on, I guess maybe it looks like a bag of cocaine or who knows, in the scanner? They wouldn’t admit it, but their equipment was having issues (I don’t have HARD evidence but the equipment seems to have frequent calibration issues) and ultimately it took bringing in some supposed supervisor/specialist who came with almost a chemistry set and tested the protein powder (they made me open it) but it was a lengthy delay AND the worst patdown I’ve ever had–he literally jammed my testicles to the point that I filed an official complaint (that went no where–they just responded with a canned response about the how and why a patdown is done). The moral of this story is I think twice before taking protein powder in my carry on (better to buy at the destination or put in checked luggage) AND I DEFINITELY do not get a massage right before a flight!

Nikki May 2, 2022 - 5:25 am

If the machine is looking for bomb making material and finds it in your lotion, that’s not a false positive. That’s a positive. The machine is working as it is supposed to.
Also, TSA random checks are randomized. If you’re in pre-and you walk through the metal detector, it lights up a certain way for a random check.
My last point is to the person worried that this article is going to tip off bad guys. After the turns out positive for a hand check, there is further screening. You can’t just tell them it’s lotion and go about your day. They’re not going to be socially engineered like that

Concerns citizen May 2, 2022 - 12:13 pm

“He didn’t share my good humor” probably because he heard the same thing 100 times in the last hour before you said it.

“TSA officer still has to fill their quota for the day” as far as i know after talking with friend of mine, there is no such thing. You probably thinking of traffic police.

Also if you are an American why you would write this article, you do understand that terrorist also have access to the internet and your article.

SharonKurheg May 2, 2022 - 4:39 pm

Don’t worry, “Conserns citizen”…the terrorists are way ahead of anything I or any other travel blogger will write. If they want to do their thing, they’ll figure out a way to try. TSA’s been pretty good at stopping them, so…

Amelia August 6, 2022 - 4:05 am

Sausages. Learned this from a very friendly TSA agent in San Jose. A whole salami from Molinari apparently looks just like a pipe bomb on x-ray and you hit the detectors for nitrates. Other cured meats do the same, I’ve since learned.
I am fortunate that they’ve always been polite and respectful with me. Probably because I treat them like they’re just doing their job. Once they located the salami, there was a nod and an “Ahh yes.” And then i was sent on my way. Both domestically and internationally.

dee May 13, 2023 - 3:52 pm

My small salt grinder is now getting taken out of my bag and 5 pieces of yellow paper are put down then my salt is grinded on to each piece of paper..Then they pull out a bottle of a chemical and they put 2-3 drops on each paper to see if it is cocaine- i guess… It never turns any color but since it is “organic” it must be regs as of feb..My poor salt grinder has been checked so many times it is almost empty and now has to stay home.. Bummer

Mango July 29, 2023 - 10:52 pm

I was selected once for a cell phone swab in the TSA Precheck line, but didn’t test positive.

In Toronto, they swabbed my backpack down and I got tested positive for explosives. I asked the operator about it and he said don’t worry, the test is super inaccurate.

fyi August 28, 2023 - 9:24 am
Dec. 2002
Explosives Detection Systems
TSA meets a key mandate of the Aviation and Transportation Security Act by deploying explosives detection systems nationwide to screen all bags for explosives.


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