We used to sell refills. We stopped, and the reason is a word that comes up a lot on this blog: biofilm. Once bacteria settle into a bottle, a pump or a dispenser, they build a protected layer that survives washing, survives bleach, and in hospitals has even survived inside antibacterial soap and hand sanitizer. Pouring fresh product into an old bottle feeds that layer instead of starting clean.
What biofilm is, and why a bottle is a perfect home for it
Biofilm is a community of bacteria that sticks to a surface and wraps itself in a slimy matrix it produces. That matrix shields the bacteria inside from cleaning agents and preservatives, which is why biofilm is so hard to remove once it forms. We've written about it in your clothes; it forms the same way on plastic and metal.
A bottle you refill has everything biofilm needs: moisture, a steady food supply, and hard-to-reach places like the pump tube, the valve and the threads of the cap. Every time you press a pump, it pulls air (and whatever is in it) back inside to replace the product that came out.
What researchers found in refillable soap dispensers
- About 1 in 4 public dispensers were contaminated. University of Arizona researchers sampled 541 refillable soap dispensers in restrooms across five US cities; roughly a quarter contained heterotrophic and coliform bacteria, at very high counts (Chattman et al., J Environ Health 2011).
- Washing with contaminated soap left hands dirtier. In an elementary school where all 14 refillable dispensers were contaminated, Gram-negative bacteria on students' and staff's hands went up about 26-fold after washing. When the dispensers were replaced with sealed-refill units, none were contaminated after a year (Zapka et al., Appl Environ Microbiol 2011).
- Refillable pumps vs sealed dispensers: 70% vs 11%. In 104 hotel-room soap dispensers in Germany, 70% of refillable pump dispensers were contaminated versus about 11% of non-refillable ones. Species included Pseudomonas, Serratia marcescens and Klebsiella. The researchers traced the entry route to the pump's pressure release, the opening that lets air back in (Lucassen et al., 2023).
Cleaning the bottle doesn't fix it
This is the finding that changed my mind. Montana State University's Center for Biofilm Engineering tested how to rescue contaminated bulk soap dispensers. They found biofilm on the inside surfaces of every type tested: plastic counter-mounted, plastic wall-mounted, and stainless steel. Then they scrubbed and disinfected them, including a 10-minute soak in a strong bleach solution. Within 7 to 14 days, bacteria in the soap were back at the same levels as before. The authors' conclusion: cleaning and sanitizing a contaminated dispenser has only a temporary effect (Lorenz et al., Biofouling 2012).
If a bleach soak in a lab can't clear it, rinsing a bottle at home and topping it up won't either.
Even antibacterial soap and hand sanitizer aren't immune
You'd expect a product designed to kill germs to protect itself. Hospital outbreak reports say otherwise:
- Antibacterial soap. A fatal Pseudomonas aeruginosa outbreak in an Italian hematology unit was traced to a heavily contaminated dispenser of triclosan-based disinfectant soap. Pseudomonas is naturally resistant to triclosan, so the "antibacterial" soap became the source (Lanini et al., PLoS One 2011).
- Liquid soap in a newborn ICU. A Serratia marcescens outbreak among infants in a French neonatal intensive care unit was traced to a liquid soap bottle dispenser. The authors recommended "airless" dispensers that don't draw air back in (Buffet-Bataillon et al., J Hosp Infect 2009).
- Hand sanitizer. In 2021 the FDA announced a recall of an alcohol-free antimicrobial hand sanitizer contaminated with Burkholderia cepacia complex and Ralstonia pickettii (FDA).
- Alcohol antiseptic. One of the largest single-source hospital bloodstream outbreaks on record, 361 patients over seven years in Beirut, came from an alcohol skin antiseptic diluted with contaminated tap water (Nasser et al., Infect Control Hosp Epidemiol 2004).
Reviews of these outbreaks keep naming the same habits as risk factors: topping up containers, reusing or poorly reprocessing them, and diluting products with tap water (Weber et al., Antimicrob Agents Chemother 2007; Lompo et al., Hygiene 2023; Baba et al., Infect Control Hosp Epidemiol 2025). Refilling is exactly that.
Why this matters more for intimate products
A hand soap gets rinsed off. Our products are used on the vulva, the perineum and around the anus, and some stay on the skin. Those are the places where we're trying to protect a healthy microbiome, not seed it with whatever has grown in a bottle.
There's also a formulation problem. We use gentle preservatives on purpose, because harsh ones irritate sensitive skin and disrupt the flora. A gentle preservative system is designed to protect a product in its own sealed bottle, through normal use. It isn't built to fight an established biofilm that's already living in an old container. To make refills safe, we'd need much stronger preservatives, which is the opposite of what we make.
So each product comes in a fresh bottle, filled once.
What you can do
- Use each bottle until it's empty, then recycle it. Please don't top it up with the new one.
- Keep the cap closed and the pump clean, and don't let water get into the bottle in the shower.
- The same goes for any soap at home: a sealed or single-use refill is safer than pouring new soap into an old dispenser.
- Use water-based products (shampoos, washes, cream, etc.) within 6-12 months after opening.
- We recommend you finish opened Zerotaboos products within six months.
Summary
- Refillable soap dispensers are frequently contaminated, and washing with contaminated soap can leave more bacteria on your hands, not fewer.
- Biofilm inside a dispenser comes back within one to two weeks, even after a bleach soak.
- Hospital outbreaks have been traced to antibacterial soap, liquid soap, sanitizer, and alcohol antiseptics in reused or diluted containers.
- That's why we don't sell refills: every ZEROTABOOS product goes into a new bottle, filled once.