As someone who lives with celiac disease and eats strictly gluten-free, Iโm always on the lookout for tools that help me eat with more confidence.
For many years, I championed Nima Sensor, a portable gluten-detecting device that allows you to test a small piece of your food for hidden gluten. While I loved the company’s original founders, the new leadership team that took over in 2020 has left much to be desired.
At that time, the company went dark for almost a year, and then, when it reemerged in 2021, it struggled to provide consistent inventory to its loyal customers. In 2024, the website disappeared for months, and the company issued zero communications. This made many of us question the company’s leadership and long-term survivability.
That’s why, when I heard about the new LEO tester a few months ago, I was filled with hope. It’s an at-home testing device with a different “buffer” solution than Nima, and it was co-founded by two people, Seaton and Jill Smith, who both have celiac disease and a son with celiac, too. They also founded GF Harvest, a once popular purity protocol oats brand, and they live a strict gluten-free lifestyle. (They are no longer associated with GF Harvest.)
The company sent me a handful of testers to play with, and while I tried one of them recently, I hadn’t given LEO a rigorous test to ensure it worked as promised until now.
What Is LEO?
LEO stands for Love Eating Out. It’s a disposable gluten tester designed to help you quickly detect gluten in food before you take a bite. It claims to detect gluten down to 10 parts per million (ppm) in less than three minutes. It looks and works similarly to a COVID or pregnancy test.
The directions on the packaging advise users to use the provided sterile swab (it looks like a Q-tip) to brush various parts of their food, then put the swab in a solution, swirl it around for 30 seconds, and squeeze out three drops of the solution into the tester.
For my first test, I tested a certified gluten-free product, a Whoa Dough chocolate chip cookie dough bar. It contains oats, which, as every gluten-free person knows, is a controversial ingredient.
A line above the O is the control, which means the tester is working. A line above the E means it contains below 10 ppm of gluten and would be considered “gluten-free.”
While the line above the E was clear to the naked eye (see below), meaning it didn’t contain gluten, the folks at LEO have since advised me to use the app to scan the device and allow AI to interpret the results. Fair enough.
The Gluten Free Watchdog’s Findings
Before I could test another item, the Gluten Free Watchdog came out with a report that shook the gluten-free community.
The Watchdog is no friend to testing devices, and her reasoning for this is for another discussion. However, her latest assessment of LEO has legs. She tested wheat bread and found variable results and flaws in the instructions provided by LEO.
Putting LEO to the Test
I decided I needed to do a rigorous assessment of LEO on my own, so I went to my parents’ house in search of gluten that I could test with my LEO testers.
Test 1: I used the wet swab to firmly swipe the inside of a hoagie roll several times, gathering a few crumbs on the swab. I dipped the swab in the solution and squeezed and swirled it for 30 seconds, then added a few drops of the solution to the tester.
Results: There was a faint line above the E (the instructions say a line above the E indicates it doesn’t contain gluten). I scanned it with the app, and the app said the sample was gluten-free, even though I knew it wasn’t. LEO clearly failed to find gluten in something that 100% contained gluten. A bust!
Test 2: I placed a small piece of the hoagie roll inside the solution, let it sit for 30 seconds, shook it, and then added three drops to the tester. I waited three minutes for the results.
Results:ย There was no line above the E, which would have indicated it was not safe to eat. LEO showed that the sample clearly contained gluten. The app confirmed that this sample contained gluten.
You can see from the LEO testers below that there is a line above the E only when I swabbed the bread (indicating it’s gluten-free) vs. no line above the E for when I placed an actual pinch of bread inside the solution (indicating it contains gluten).
I contacted the owners of LEO and shared my findings. We had a long phone discussion, and the founders assured me that they conducted independent testing of their testers before going to market. They said my results, along with the Watchdog’s results, surprised them.
The good news, however, is that the Smiths were receptive to this feedback and eager to make things right.
They said they updated their instructions and testing protocols to better account for testing hard and dry foods, such as the hoagie roll. The new instructions can now be found on their website. And they are also updating the instructions on their packaging.
They now advise users to place a small pinch of dry food (bread/crackers/cookies) directly into the solution vs. only swabbing the food. Based on our experimentation, we believe this will ensure more accurate results.
The Smiths sent me the following statement:
“We want to sincerely apologize for any confusion and frustration this issue may have caused. After a thorough review over the past five days, we learned that dry or hard products – like bread, hard rolls, or cookies – donโt allow the swab to collect enough of a sample for a proper test in one of the batches we made.
“We found that placing a 3 mg pinched sample in the vial allows the test to work correctly and am adjusting our testing steps to include this for all of our testers now. The updated testing steps will be emailed to all of our customers and posted publicly.
“We understand how important trust is to our LEO customers, and we are committed to earning that trust back. Our priority is always integrity over sales, and we believe this revised testing approach will provide more accurate and dependable results.”
Testing Breadcrumbs with LEO
I also tested gluten breadcrumbs and gluten-free breadcrumbs to see how they fared with LEO, and the results appear accurate.
According to LEO, the gluten breadcrumbs contained gluten, and the gluten-free breadcrumbs did not. I could visibly see bits of breadcrumbs in the testing solution.
One other concern that came to light is that my “control” test seemed wonky. I added the solution to the LEO tester without mixing it with any crumbs. There was no line above the E (contains gluten), yet the solution should have been gluten-free and therefore displayed a line above the E.
I asked Smith about this, and he said that it’s essential that I shake the vial because the solution separates. I performed another control test where I didn’t put anything inside the vial but shook it first, then added drops to the tester. The test came back with a line above the E and O.
LEO Show Promise, But Needs Work
While the LEO tester likely works and shows promise as an in-home gluten-testing method, users should be careful when using it until the company updates its testing procedures and packaging. I might even suggest that the company publish additional third-party testing data.
Here are my suggested improvements:
(1) Increase the collection sample size for dry and hard foods.
Swabbing food is not sufficient to get an accurate result using LEO. A small sample (just a pinch) of the food should be placed in the solution instead. While this is true for dry and hard foods, I would need to see further testing of other types of food (gummies, hard candies, sauces, etc.).
(2) Educate users on how to use LEO properly.
The instructions provided by LEO on the packaging aren’t enough to help people perform an accurate at-home test. Tests should come with additional information about accurately testing different kinds of food.
As discussed, hard and dry foods require a pinch of the food in the testing solution. I also learned that pasta should be cooked before it’s tested. These nuances are important for people who need to learn how to be responsible users.
(3) Make the result interpretation more straightforward.
The instructions on the packaging say that if you see a line above the E, it’s safe to eat and contains less than 10 ppm of gluten. If you don’t see a line, the company says, “Do not eat.”
One issue is that the line is sometimes dark and sometimes faint, and it’s hard to interpret what the different shades mean and if a faint line is okay.
Smith says LEO contains an antibody that can have up to a .05 variation (purity), and depending on that purity, that will make the line a different color.
When I tested wheat bread, the line over the E was light but visible. That must have meant it contained greater than 20 ppm of gluten, according to the LEO Line Contrast Scale (see below).
While this is helpful, it’s open to interpretation. The color contrast between 20 ppm and 11 ppm is subtle, but it is clear that the darker the line, the less gluten it contains.
(Is it just me, or should the darker color line mean a positive gluten test? My brain keeps telling me the opposite of what is true.)
The LEO team suggested I use the LEO app to interpret the results better. It’s AI-trained to read the results more accurately than the naked eye. I can’t help but wonder if the shade of the line will change depending on the lighting or how long the test is left to sit. I noticed that the line will darken with time. Does this mean results past three minutes are inaccurate or more accurate?
The Bottom Line:
Overall, the LEO tester shows promise. It’s lightweight, portable, and doesn’t require an expensive testing device like Nima. It’s also run by people who care about the celiac community and are receptive to feedback.
That said, LEO needs more work and clearer instructions before it can be fully trusted. Users of LEO should educate themselves fully before using it, and use it with caution until improvements are made.
Of Note:
LEO cannot detect gluten in the following foods:
- Alcohol
- Pure Xanthan Or Guar Gum
- Fermented Items Like Beer
- Hydrolyzed Foods such as soy sauce and malt extract / ๏ฌavoring
LEO testers are single-use, disposable testers. Depending on how many you buy upfront, they will cost $5.31 – $9.92 per tester, not cheap! You can find them online at leoverified.com.
Additional Reading
Did Nima Sensor Go Out of Business?
The Allergy Amulet Gluten Detecting Device
Do the Glutrust Gluten-Detecting Testers Work? An Honest Review
Just make sure you add a pinch of dry/hard food to the solution. It should be accurate then.
helpful information! I bought some but have not used them yet and it seems it might be a bit challenging right now to ensure accurate testing. Hopeful for the future though!