As far as medical discoveries go, antibiotics are one of the crowning achievements of the 20th century. Since penicillin was discovered in 1928, antibacterial drugs have saved millions of lives and laid the foundations for all sorts of other treatments. In recent years, however, as antibiotics have crept into everything from hand soap to catheters, researchers have become concerned that frequent exposure to these chemicals may be making bacteria stronger. As it turns out, bacteria aren’t the only problem: new research suggests that potentially deadly fungal infections are becoming more drug resistant as well.

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Some people may think of fungal infections as relatively benign, such as athlete’s foot or yeast infections. And while some of these woes are easily treated, there are many other fungal infections that can lead to much more serious health problems, Robin McKie reports for The Guardian.

“Fungi can spread through patients’ bodies and into their spines and brains,” Gordon Brown, head of Aberdeen University’s new Center for Medical Mycology, tells McKie. “Patients who would otherwise survive treatments are dying every year from such infections.”

Fungal infections are especially dangerous for people with compromised immune systems, such as those who are undergoing treatment for cancer or HIV/AIDS, are recovering from major surgeries, or are living with a chronic condition like cystic fibrosis. But while there is a wide variety of antibacterial treatments available, there is only a handful of antifungal treatments out there, McKie reports.

“There are more than 20 different classes of antibacterial agents. By contrast, there are only four classes of antifungal agents,” Adilia Warris, co-director of the Center for Medical Mycology, tells McKie. “Our armory for dealing with deadly fungi is much smaller than the one we have for dealing with bacteria.”

That makes this new research about fungi's potential antibiotic resistance even more concerning. The problem with antibiotics (both antifungals and antibacterials) is that the more frequently they are used, the more they weed out the susceptible organisms. That leaves the more drug-resistant organisms alive and able to reproduce, which can result in passing down the strongest genes.

It’s not just that people should stop using antibiotic soap or carrying hand sanitizer with them everywhere. The problem is that humans are using so many of these antibiotics that they are getting into the environment and affecting it. One popular antibacterial called “triclosan” is commonly found in antibiotic soaps, but it is also used as a pesticide, immunologist Tirumalai Kamala writes for Quora. Triclosan is used in so many products that it is nearly impossible to keep it out of the natural world, where it messes with animals’ microbiota and even the workings of our cities’ sewage systems, which rely on healthy microbes to break down waste. Similarly, the overuse of fungicides on crops has researchers concerned about breeding drug-resistant strains, some of which may already be showing up in hospitals around the world, Maryn McKenna reports for National Geographic.

There’s no easy solution to fighting the spread of drug resistant pathogens, but researchers are taking the first few steps. More lab time is being devoted to figuring out ways to combat fungal infections, while some countries have either banned triclosan outright or are considering it. In any case, it might be worth thinking twice the next time you’re considering buying a bottle of antibacterial soap at the supermarket.