When you think about antibiotic resistance, doctors writing too many prescriptions or rampant antibiotic use in agriculture probably spring to mind. However, one of the culprits could be sitting near your bathroom sink.

New research has shown how a common ingredient in toothpaste and hand wash could be contributing to antibiotic resistance and the creation of “superbugs”.

The chemical in question is triclosan. This ingredient is added to over 2,000 hygiene products – namely hand soaps, shower gels, and toothpaste – to slow down or prevent bacterial growth. In the case of toothpaste, it can even help ward off gingivitis, so it's a pretty useful ingredient.

Strangely enough, however, triclosan is not an antibiotic per se, but an antimicrobial agent. Scientists were actually unaware that other chemicals could also induce antibiotic resistance until now.

As explained in the journal Environment International, scientists have now shown how oxidative stress induced by triclosan can lead to mutations in certain genes of germs such as E. Coli. By chance, some of these mutations allow the bacteria to become extra tough against drugs. For example, one mutation alters a gene that’s associated with membrane permeability.

The problem is that this ingredient can potentially be washed away down plugholes then into wastewater and sewers. Here, the chemical is able to accumulate at high levels while also being swamped with bacteria, resulting in the perfect storm.

"Wastewater from residential areas has similar or even higher levels of antibiotic-resistant bacteria and antibiotic resistance genes compared to hospitals, where you would expect greater antibiotic concentrations," Dr Jianhua Guo from the University of Queensland said in a statement.

"We then wondered whether non-antibiotic, antimicrobial chemicals such as triclosan can directly induce antibiotic resistance.

"These chemicals are used in much larger quantities at an everyday level, so you end up with high residual levels in the wider environment, which can induce multi-drug resistance. This discovery provides strong evidence that the triclosan found in personal care products that we use daily is accelerating the spread of antibiotic resistance."

In 2017, the US Food and Drug Administration (FDA) banned the use of triclosan in soaps and some antiseptic products, however, it's still used in many brands of toothpaste. It's also still widely used in soaps in many other parts of the world.

Now the link to antibiotic resistance is clearer, the researchers hope their study could be used to reevaluate our use of such chemicals.

“While the US Food and Drug Administration (FDA) has banned the use of triclosan in antibacterial soap, the previous lack of unequivocal evidence prevented such a policy being adopted in other countries," added co-author Professor Zhiguo Yuan.