How can hand sanitizer make you sick?

During the COVID-19 pandemic, disinfectants became our shield. Hand sanitizers, disinfectant wipes, and antimicrobial sprays became part of daily life. They made us feel safe. Even today, they are everywhere: in homes, hospitals and public places.

But there is a hidden cost. The chemicals we rely on to protect us may also protect us Unknowingly helps germs develop resistance And protect yourself from antibiotics.

QACs: Chemicals present in most disinfectants

The most common active ingredients in disinfectants are quaternary ammonium compounds (QACs). They are found not only in the wipes, sprays, and liquids we use to clean surfaces at home and in hospitals, but also in everyday products like fabric softeners and personal care products.

Nearly half of the products on the U.S. Environmental Protection Agency’s (EPA) List N of disinfectants effective against SARS-CoV-2 and List Q for emerging viral pathogens contain QACs.

Due to their widespread use, QACs enter wastewater treatment plants in substantial quantities, with effluents and sewage sludge being the main routes through which QACs are released into the environment.

Within wastewater treatment plants, more than 90 percent of the QACs are typically removed, but small amounts remain in the wastewater and reach rivers and lakes, where they accumulate.

Once QACs enter the environment, they encounter microbial communities, networks of bacteria, archaea and fungi that recycle nutrients, purify water and support food webs.

Given that QACs are designed to kill microbes, it is no surprise that they can impact the environment. Yet microbial communities are remarkably adaptable; Some die, but others survive and develop resistance.

paradox of security

Unlike antibiotics, which target specific cellular processes, QACs attack microbes and viruses in multiple ways, damaging cell walls, proteins, and lipids. This broad attack makes QACs powerful disinfectants.

However, microorganisms are resourceful. Faced with these chemicals, some strengthen their cell membranes, expel toxins or form protective biofilms. These adaptations not only help them survive QAC, but growing evidence suggests they may also increase antibiotic resistance.

At the genetic level, QAC resistance genes are often carried on mobile DNA, segments of genetic material that can move between different bacteria. When these elements contain both QAC and antibiotic resistance genes, resistance travels together and can spread through bacterial communities, a phenomenon called co-resistance.

In other cases, a single defense mechanism protects against both QAC and antibiotics, a process known as cross-resistance. The widespread and increasing use of QACs amplifies these mechanisms, creating greater opportunities for resistance to spread. This, in turn, establishes pathways through which antimicrobial resistance Humans can access pathogens, contributing to the global rise of antibiotic-resistant infections.

According to a new report from the World Health Organization (WHO), antimicrobial resistance is “critically high and rising” globally: in 2023, one in six laboratory-confirmed bacterial infections responsible for common diseases worldwide were resistant to antibiotic treatment. Between 2018 and 2023, resistance increased in more than 40 percent of the monitored pathogen-antibiotic combinations, with an average annual increase of five to 15 percent.

WHO estimates that in 2019, antibacterial antimicrobial resistance directly caused 1.27 million deaths and nearly five million more deaths worldwide. What starts as a household cleaning choice can expand to the outdoors, linking our everyday habits to one of the most pressing public health challenges of our time.

Antimicrobial resistance is often viewed as a clinical problem caused by antibiotic misuse, but it starts much earlier in homes, wastewater, rivers, lakes and soil. These are battlefields where microbes share resistance traits and adapt to human-caused chemical pressures. Once resistance arises, it may come back to us.

At its core, the disinfectant dilemma is a feedback loop: We disinfect to prevent disease, but the chemicals we rely on may quietly make germs harder to control.

clean rethink

This doesn’t mean we should stop disinfecting. Disinfectants play an essential role in infection control, especially in hospitals and high-risk settings where their benefits far outweigh their risks. The issue lies in their overuse in everyday life, where “clean” is often equated with “microbe-free”, regardless of necessity or consequence.

We rarely consider that cleaning does not end when the surface looks clean. Some disinfectants remain active long after use, continuing to shape microbial communities beyond the intended moment of control. QACs are a clear example: they persist in the environment, exposing microbes to low, long-term selective pressures that can promote the evolution of resistance.

Other disinfectants, such as alcohol and bleach, may carry different, but still meaningful environmental risks, underscoring the need for risk assessments that more clearly integrate long-term ecological consequences.

Ultimately, the disinfectant dilemma reminds us that managing germs is as much about ecology as it is about chemistry. To clean responsibly, we need to think beyond what kills germs today and consider how our choices shape the microbial world we face tomorrow.