Client Success Stories

Learn About Microbiology

Microbiology Basics

Microbiology Photos

Introduction to Hand Sanitizers

By Benjamin D. Tanner, Ph.D., President, Antimicrobial Test Laboratories

Definition: Hand Sanitizers are liquid formulations designed to kill bacteria quickly on the skin of the hands.

Liquid hand sanitizers - mostly alcohol-based gels - have enjoyed an explosion in popularity in the last 10 years. If you have traveled by airplane or set foot in a schoolroom in the US lately, surely you have seen hand sanitizers in use!

Hand sanitizers are believed to bring consumers much of the microbiological benefit of handwashing without the need for running water and a sink. Like many other antimicrobial products, it is challenging from a scientific perspective to isolate the effect of hand sanitizer use as related to reduced illness. So understandably, the perceived benefit of hand sanitizers is based mainly on their germ killing capabilities in the laboratory.

Handwashing and hand sanitizers both reduce carriage of potentially dangerous microorganisms on the hands, but do so in very different ways. Handwashing - whether done with "antibacterial" soap or plain soap - physically removes microorganisms from the skin. Hand sanitizers reduce levels of microorganisms by killing them chemically.

The antimicrobial chemical lineup in US hand sanitizers is limited by two factors. The first is US Food and Drug Administration (FDA) regulations, which are discussed further below. The second is technical in nature - hand sanitizer chemicals must do their job within a very brief period of time to produce the necessary effect and must be perfectly safe on skin. Thirty (30) seconds is considered the upper reasonable time limit to produce a meaningful redution in microorganisms on the hands.

Companies interested in marketing a hand sanitizer in the United States will benefit from becoming familiar with the FDA Tentative Final Monograph, which sets out current US hand sanitizer regulations.

Aspects of the FDA Tentative Final Monograph follow, with certain excerpts hightlighted and discussed in further detail. Remember, the tables and sections discussed below come from the tentative final monograph, so there's room to customize and streamline studies for submission to regulatory agencies.

FDA TFM Excerpt #1: FDA-Known Topical Antimicrobials, Data Requirements

The table above lists various chemicals which may be used to power various types of topical antimicrobials and provides information about whether safety and efficacy testing are required. The Roman numerals in the table identify the product category, and the presence of "S" and/or "E" indicates whether safety and/or efficacy testing is required.

If there is one thing to learn from the table above, it is that a product may or may not need efficacy or safety testing, depending on its active ingredient. For example, as Antimicrobial Test Laboratories interprets the table, 60-95% ethanol hand sanitizer formulations do not require efficacy testing. Note: it is a good idea for companies to do confirmatory efficacy testing, even if not required by FDA.

If efficacy testing of your product is required, exact requirements are detailed in the page below:

FDA TFM excerpt #2: Page 31444, Detailing Tentative Efficacy Test Guideline

As the highlighted sections of the document show, the Tentative Final Monograph suggests testing across a broad array of bacteria and fungi using both MIC and time-kill methods, which are the two in vitro components of the efficacy testing process. It also indicates that a clinical "glove test" is performed, typically upon completion of the MIC and Suspension Time-Kill studies. The in vivo portion of efficacy testing is carried out using a bacterium called Serratia marcescens, which is inoculated onto the hands of volunteers and then recovered by massaging the hand in a broth filled, sterile glove.

Antimicrobial Test Laboratories thanks you for taking the time to learn about hand sanitizers! If you are ready to get started with a confirmatory efficacy study for an ethanol-based hand sanitizer or get started documenting the efficacy a new Category II or Category III hand sanitizer, we encourage you to give us a call or get a price quote.