Amazon reviews can be enlightening and entertaining, and sometimes—as author Rachel Sharp revealed on Twitter this weekend—concerning. On Sunday, Sharp tweeted some reviews left on Amazon listings for antibiotics intended for pet fish, and they revealed something disturbing: People are buying these antibiotics to take themselves.

Here's everything you need to know about this bizarre trend:

People Write in Code

In the reviews for products such as Fin Mox and MoxiFish—both billed as fish doses of the antibiotic amoxicillin—consumers write in lightly veiled code how effective the medication was for their "fish:"

Basically every brand of fish antibiotic on the site has some form of these reviews, which make it blatantly obvious that people are taking, intend to take, or are pretending to take these animal medications themselves to treat human ailments.

A Symptom of US Healthcare?

Sharp suggested that people taking antibiotics meant for guppies is a sign of how inaccessible and expensive American health care has become. In fact, some reviews even allude to this, noting that the fish pills are a "great alternative to racking up debt at the fish hospital."

Though generic antibiotics are often very affordable, or even free, at pharmacies, the cost of visiting a doctor to get a proper prescription can be prohibitive for some people, particularly people who don't have health insurance. Studies have shown it's common for people to keep old prescriptions of antibiotics to use in the future without a diagnosis, or even take their pets' antibiotics.

Online, there are plenty of posts from people asking about or recommending using medication intended for animals as an alternative to getting a proper prescription. It's not entirely surprising that they might also be turning to fish antibiotics from Amazon.

With our better understanding of antibiotic resistance, doctors have also become more judicious in doling out antibiotics. Studies show that people are frustrated and dissatisfied when they go in hoping for penicillin and are told no, which could be another driver behind the aftermarket on fish meds.

This Is a Terrible Idea

For a number of reasons, it's not a good idea to take random fish antibiotics you bought on the internet. First of all, not every infection is a bacterial infection, which are the only kind antibiotics treat. Even if you have similar symptoms to a previous infection, like say bronchitis, without seeing a doctor, you don't know if it's bacterial, viral, parasitic, or something chronic.

Different infections call for different antibiotics, too, and doses depend on the individual and the infection: something that's difficult to determine on your own. Plus, fish antibiotics online may not even be what they say they are. The Food and Drug Administration hasn't approved these, so they're not regulated, which means you have no idea what you're really getting.

But perhaps most importantly, using antibiotics incorrectly (like taking the wrong dose or the wrong type of medication), or when you don't need them, contributes to antibiotic resistance. The more we abuse antibiotics unnecessarily, the more bacteria are exposed to our best defenses and can evolve to evade them. It's part of the reason why antibiotic-resistant superbugs are on the rise.

Some Buyers Might Not Be Taking Them...Yet