You might think it’s a prank. Or maybe a crime. Honestly, for most people, the idea of sending feces in the mail sounds like the punchline to a very bad joke or something pulled straight from a revenge subreddit. But the reality is way more boring—and way more important—than the internet would have you believe. Every single day, thousands of these packages zip through the USPS and FedEx systems. Most of them aren't sent out of spite. They’re sent for science.
It’s gross. We can admit that. But if you’re looking into this because you’re curious about the legality of "prank" services or because your doctor just handed you a stool collection kit, you need the facts. The line between a legitimate medical diagnostic and a federal felony is razor-thin. It basically comes down to intent and packaging.
Why People Are Actually Sending Feces in the Mail
Most of the time, this happens because of colon cancer screenings. Programs like Cologuard have completely changed the landscape of preventative medicine. Instead of a traditional colonoscopy—which, let’s be real, nobody actually wants—patients can collect a sample at home and ship it to a lab. Exact Sciences, the company behind Cologuard, has processed millions of these kits.
It isn't just cancer, though.
Research into the human microbiome has exploded over the last decade. Companies like Viome or Sun Genomics offer kits where you send in a sample to get a breakdown of your gut bacteria. Scientists are finding that the "bugs" in your gut might influence everything from your mood to how you process sugar. Because of this, the postal service has become a literal pipeline for biological data.
Then there’s the Fecal Microbiota Transplant (FMT). It sounds wild, but it’s a life-saving treatment for Clostridioides difficile (C. diff) infections. OpenBiome, a major stool bank based in Massachusetts, paved the way for the rigorous screening and shipping of healthy donor samples to hospitals nationwide. In these cases, the "mail" is actually a highly regulated cold-chain logistics operation.
The Legal Nightmare of "Prank" Shipments
Here is where things get dicey. You’ve probably seen those websites. They promise to anonymously mail a "poop gift" to your enemies. They claim it’s all "legal" because it’s meant as a novelty.
📖 Related: Why the EMS 20/20 Podcast is the Best Training You’re Not Getting in School
Don't believe them.
Sending feces in the mail with the intent to harass, annoy, or threaten someone is a crime. Full stop. In the United States, 18 U.S. Code § 1716 governs "Injurious articles as nonmailable." While the law specifically mentions poisons and explosives, it also covers "all other natural or artificial articles, compositions, or materials which may kill or injure another, or injure the mails or other property."
Biohazards fall under this. If a package leaks and a postal worker gets exposed to potential pathogens like E. coli or Hepatitis, the sender is looking at serious federal charges. The USPS Prohibited, Restricted, and Perishable Mail regulations (Publication 52) are incredibly strict about how "Clinical Specimens" must be handled.
If you send a sample without the proper triple-packaging—leak-proof primary container, leak-proof secondary packaging, and a rigid outer shipping container—you are breaking the law. Prank sites rarely follow these medical-grade standards. If the box smells or leaks? You've just flagged yourself for a federal investigation.
How the Pros Do It: The USPS Rules
If you actually have to do this for a medical test, there’s a specific protocol. You can't just toss a plastic baggie into a manila envelope.
The USPS categorizes these items as "Category B" infectious substances (UN3373). This means they aren't expected to cause permanent disability or life-threatening disease in healthy humans if exposure occurs, but they still need respect.
👉 See also: High Protein in a Blood Test: What Most People Get Wrong
- Primary Receptacle: This is the vial or container holding the sample. It must be leak-proof.
- Absorbent Material: There must be enough material (like paper towels or specialized pads) to soak up the entire contents if the primary container breaks.
- Secondary Packaging: Another leak-proof layer, like a sealed biohazard bag.
- The Outer Box: A sturdy cardboard box. No padded mailers.
The box must also be labeled correctly. Usually, medical kits come with a pre-printed "Exempt Human Specimen" label. This tells postal workers that as long as the box isn't damaged, it's safe to handle.
The "Mailing Poop" Misconception
People often ask: "Is it illegal to mail poop?"
The answer is: It depends on why you're doing it.
If you are a farmer sending a manure sample to a soil-testing lab, that’s business. If you are a patient sending a sample to a lab, that’s healthcare. But if you are sending it to your ex-boss because they fired you? That is harassment. The United States Postal Inspection Service (USPIS) does not have a sense of humor about this. They track these things. They have labs. They have investigators.
Think about the 2018 case in Michigan where a woman was charged for mailing feces to her neighbors. It wasn't just a "gross prank." It was a series of charges involving stalking and illegal mailing of hazardous materials.
The Science of What’s Inside
What are labs actually looking for? It's not just "gross stuff." They are looking for DNA.
✨ Don't miss: How to take out IUD: What your doctor might not tell you about the process
In the case of colon cancer, they look for hemoglobin (blood) and specific DNA mutations that shed from polyps in the colon. For microbiome testing, they sequence the 16S rRNA gene to identify exactly which species of bacteria are living in your gut.
It’s actually incredible technology. We’ve reached a point where a tiny sample sent through the mail can predict disease years before symptoms appear. This is why the USPS allows it—the public health benefit of these tests outweighs the "ick" factor of the contents.
Practical Steps If You Need to Ship a Sample
If a doctor has asked you to do this, don't overthink it, but do be precise.
First, read the instructions three times. Most kit failures happen because the patient didn't seal the vial correctly or forgot to include the paperwork. If the lab can't verify who the sample belongs to, they have to destroy it as biohazardous waste.
Second, check the temperature requirements. Some kits require you to ship them immediately. Others include a preservative liquid that stabilizes the DNA at room temperature. If your kit requires a cold pack, make sure you don't drop it in a blue collection box on a Friday afternoon in July. It will sit in the heat all weekend, and the sample will be useless.
Third, use the provided shipping label. These are usually "Priority Mail" or "FedEx Clinical Pak" labels. They ensure the package moves through the system quickly.
What to Avoid
- Never use your own packaging unless explicitly told to by a lab.
- Never ship a sample that is leaking. If it leaks, start over.
- Avoid drop boxes if the weather is extreme. Hand the package directly to a clerk or a driver if possible.
Sending biological matter is a responsibility. Whether it's for a gut health check or a serious medical screen, the postal system is a vital link in modern medicine. Treat the process with the same level of care you'd want a lab technician to use when they open your package on the other end.
If you're dealing with a medical kit, ensure the "Exempt Human Specimen" marking is clearly visible on the outer box. Double-check that the primary container lid is threaded correctly and tightened—cross-threading is the number one cause of leaks. Once the package is sealed, drop it off at a staffed USPS location or scheduled pickup to minimize the time the sample spends in an uncontrolled environment. For those looking at microbiome testing, ensure you haven't taken antibiotics in the timeframe specified by the lab (usually 2-4 weeks), as this will completely skew your results. Following these technical steps ensures your data is accurate and your shipment stays within federal guidelines.