Ask ACI: Hand Soap Dilution

Q. Can you safely dilute hand soap?

A. No. For optimal safety, you should not dilute hand soap, unless it is a concentrated product intended to have water added for use. 

We’ve all been there: you go to wash your hands and realize you’re down to the last dregs of your liquid hand soap. You may be tempted to add water to the soap dispenser. But there’s a good reason not to.

Liquid soap is made up of a precise combination of ingredients that work together to effectively lift dirt and grime from your hands and help destroy many kinds of bacteria and viruses, including the new coronavirus. Extra water throws off the balance of these ingredients and reduces their strength, making the soap less effective.

Think of it like baking. Adding extra milk or flour to a recipe can drastically change its outcome. While it might be okay to dunk cookies into milk after they’re baked, adding too much milk to the batter will leave you with a soggy mess.

There’s also the concern of adding bacteria to the mix. Liquid soaps contain a very strict amount of preservatives which prevent bacteria from multiplying in the dispenser. When you open the dispenser and add tap water, you may be adding bacteria as well. Plus the extra water reduces the effectiveness of the preservatives, meaning the bacteria can multiply in the soap. Studies have shown that when you wash your hands with contaminated soap, you could be increasing the number of disease-causing bacteria on your hands.

FAQ

What is liquid hand soap?

Unlike a bar soap, liquid hand soap is a detergent. It is made up of surfactants that break up dirt, grime and germs and carry it down the drain with the help of running water. It also contains ingredients like preservatives for a longer shelf life and pH adjusters to be gentle on hands. Fragrances are often added for a pleasant smell that helps reinforce good hand hygiene habits. Learn more about the chemistry of how detergents like hand soaps work.

What should you do when your liquid hand soap is running out?

The next time your liquid soap is running low, flip the bottle to get the dregs out and replace it with a new bottle of soap. If you’re using a bulk refillable soap, make sure you’re putting the same product into the original container – without extra water! If you’re out of liquid soap completely, wash your hands with bar soap instead! It does all the same things liquid soap does.

Can I dilute concentrated hand soap?

Yes, as long as you follow the product directions carefully. Concentrated hand soap is intended to have water added and is a sustainable option that reduces plastic and reduces energy used to ship water. Use clean water that is filtered, if possible. Do not use more water than directed in order to get more product, as this can affect efficacy and safety.

What are the risks of diluting hand soap?

Diluting liquid hand soap can create several risks, especially if it’s done in the original bottle and then used over time:

• Reduced cleaning effectiveness: Adding water lowers the concentration of surfactants—the ingredients that help lift dirt, oils and microbes from skin—so the soap may not clean as well.
• Preservative imbalance: Hand soaps are formulated with preservatives at specific concentrations. Dilution can weaken that preservation system, making the product less stable.
• Microbial contamination: Water, hands, sinks, or refill containers can introduce bacteria or mold. Once diluted, the product may be more likely to support microbial growth.