Russel Walters, research consultant on Kolabtree and technology inventor, provides a quick and easy guide to formulating hand sanitizer that’s FDA-compliant.
Key message: With recent rule changes, it is now easy to begin formulation and manufacture of alcohol-based hand sanitizers. Follow the new rules from the FDA and you can quickly start producing hand sanitizers.
How do hand sanitizers work?
Hand sanitizers are designed to be an alternative to hand washing with water and surfactants. Hand sanitizers reduce the viral and bacterial load on skin. They don’t necessarily kill everything, although, viruses, such as covid-19, are more susceptible. In order for a virus to infect a human host, the host needs to be exposed to a sufficient virus load, typically hundreds or thousands or tens of thousands of viral particles. Hand sanitizer dramatically reduce the viral load on the skin, and thereby reduce infections, or perhaps infection severity.
Long sustained exposure is to an infected person is best for transmission. The hands are important to sanitizer because hands are the primary contact to the outside word and then hand subsequently touch eyes, mouth, food, etc. Hand sanitizers have repeatedly been shown to slow the spread of viruses.
Hand sanitizers are regulated in most countries. In the US, the FDA has recently liberalized manufacturing rules. This is a good thing for new hand sanitizer manufacturers and formulators. It opens a legal path for new manufacturers to expand hand sanitizer supply, and it also makes formulation straightforward. Unlike skin lotions, the options are few and constraints clear.
This article will focus on the two hand sanitizer formulas that are allowed by the FDA under the recent COVID-19 guidance.
Hand sanitizer formulation – 2 choices: ethanol or isopropanol
Hand sanitizer before COVID-19: think Purell.
Manufactured at very large and FDA-registered drug manufacturers. This article covers a wider variety of approaches to formulating hand sanitizers.
New hand sanitizers after COVID-19: expanded manufacturing and production
In March 2020, the FDA issued guidance for expanded production of hand sanitizers during COVID-19. The intention was to increase production of hand sanitizer by opening up which entities could manufacture them beyond previously licensed or registered drug manufacturers. It is very specific on the formula of hand sanitizers.
The World Health Organization has released an excellent step by step guide to local production of hand sanitizers. The two formula options that the WHO recommends are the same as in the FDA guidance. Both hand sanitizer formulas are shown below.
“The hand sanitizer is manufactured using only the following ingredients in the preparation of the product”
- Either Ethanol or Isopropinal
- Glycerin
- Hydrogen Peroxide
- Sterile water
And that is it. 4 ingredients, mix them with care, and you have a hand sanitizer ready for this new post-COVID-19 world. The proportion of ingredients is also specified in volume %. Be aware of the difference between volume% and weight%. There is a big difference between wt% and vol% because different ingredients have different densities. While water has a density of 1g/cm3, ethanol has a density of 0.789g/cm3. Learn more about measuring ingredients in weight vs. volume%.
Formula 1: Ethanol (volume %)
Ethanol 80%; Glycerin 1.45%; Hydrogen peroxide 0.125%; QS water
Formula 2: Isopropanol (volume %)
Ethanol 75%; Glycerin 1.45%; Hydrogen peroxide 0.125%; QS water
QS stands for the Latin quantum satis, sufficient quantity, meaning make the rest up in water. Also note that most raw materials are not supplied as 100% pure, single ingredients. They often contain some water. Ethanol is typically sourced as 95%/5% ethanol/water, or 190 proof. You need to factor the raw material composition into your calculations.
Adding additional skin benefit ingredients and fragrance
These are explicitly not allowed under FDA guidance. Purell does contain glycerin and fragrance. Glycerin is a common and inexpensive skin benefit agent. Users tend to really like fragrances in skin care products. Both ingredients are not needed and will increase the raw material prices of your hand sanitizer. In skin care products, fragrances are often used to cover the underlying base odor, which can often have a negative odor. This is unneeded in hand sanitizers; their base odor is minimal.
Thickening hand sanitizers, increasing viscosity
Hand sanitizer gels, like Purell, use polymers to increase the viscosity. This adds some significant complications in the manufacturing. Thickening polymer are not part of the FDA formula described above, but you can read more about them the different polymeric options for thickening water/alcohol solution here. Also, Ashland is a manufacture of thickener hydroxypropylmethyl cellulose, carbomer and a few more. The two simple water/alcohol formulas above will be water thin and easily sprayable.
Sourcing of materials, and notes of caution
Sterile Water: boiling is the easiest and most likely route. Just be careful of heating and boiling water near the high proof, flammable alcohol.
Ethanol: There are a few sources of ethanol. One important note: the ethanol must be denatured, made to taste bad to avoid consumption. While states are relaxing cocktails to-go, your hand sanitizer is not to be consumed.
For additional cosmetic ingredients this ingredient search is a useful tool.
Mixing your hand sanitizer: putting it all together
This is pretty straightforward with one caveat: Passivation. If you are using a glass or fiberglass vessel to mix your hand sanitizer, then passivation is not a concern. However, if you are using a metal vessel, such as stainless steel, and you don’t know what passivation means, find out here. The short version is, in the presence of metal ions from the vessel, the hydrogen peroxide (H22) rapidly breaks down to water and oxygen.
Packing options
Ensuring that the alcohol evaporation is limited between production and use is an important consideration. The packaging must seal sufficiently. Manual pumps are explicitly allowed in the FDA guidance.
Options for natural alternatives
Ethanol is a natural product. There are natural antimicrobials; however, efficacy data on them is limited, and more importantly, hand sanitizers are a regulated product. In order to label and market a product as a hand sanitizer, the FDA guidelines must be met.
Skin safety & dealing with allergies
Hand sanitizers are likely better for the skin barrier than repeated washing with soap. Cleansing with soap often removes skin components and can disrupt the natural structure of the skin. In contrast, after killing bugs you’re the skin the alcohol in hand sanitizers rapidly evaporates and has little impact on the skin barrier. The core of your hand sanitizer formula should not cause any skin problems. Fragrance is often the source of skin irritation, especially allergenic response.
Testing
Many problems are solved if you are following the FDA guidance on hand sanitizers. There is no need to test the bug-killing efficacy of your formula. Hand sanitizers with the formulas outlined above are well proven to effectively kill bugs and be safe for the user. So you don’t have to prove this any further. After production, the alcohol level – ethanol or isopropyl alcohol – needs to be checked by physical chemistry means such as alcoholmeter or hydrometer.
More reading on hand sanitizers
- A hand sanitizer “how they work” video
- WHO guide to local hand sanitizer production
- FDA hand sanitizer guidance
- Health Canada’s interim expedited licensing of hand sanitizers
- GOJO (makers of Purell) Technical Publications
- Cosmetics & Toiletries journal
- Extensive details and background from USP
Need help with hand sanitizer formulation? Hire trusted freelance formulation chemists on Kolabtree. Post your project and get quotes for free!
Work with the author
Previously a Research Fellow at J&J, Russ has developed skin care technologies that were launched into dozens of products and 100’s of SKU’s. He is a prolific inventor with 20+ US patents and is an active researcher with 35+ scientific articles. Russ is on the advisory board of Cosmetics & Toiletries. Currently the co-founder & CTO of Somn, Russ also consultants in personal care and digital health.
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