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Yes, you can make your own hand sanitisers but mostly I wouldn’t (and haven’t).

March 15, 2020

Right now I’m at home.

My eldest daughter is sick with a virus she picked up from the little people at pre-school, not Covid 19, just hand, foot and mouth.  My youngest is in isolation due to having come in close contact with the Blue Mountain’s first (and so far only) confirmed case of this pandemic disease. She is currently well so we are feeling lucky (so far)…  Like many healthy young-ish folks I was feeling pretty nonplussed about this whole situation about two weeks ago and was happy to go about my daily business without giving it much thought.  Today things are rather different.  Today I was due to fly to a remote Aboriginal community here in Australia but that was cancelled (thank goodness) because the risk was too high – the death rate among Aboriginal communities when hit with these outbreaks is typically in double figures due to compounding health and geographical situations.  Cancelling the trip wasn’t about me, it was about them and that is pretty much what this pandemic is for the most of us – a period of self-sacrifice in order to safe the more vulnerable.  Let’s join together in playing out part and part of that involves hand sanitiser.

The last two weeks at the New Directions factory have been extremely busy as hand sanitiser orders fly in and out of the door.  On top of that I man the technical help desk, run staff training and teach classes, all of which have involved a discussion around the chemistry, functionality and safety of alcohol sanitiser solutions.

I have seen various blog posts and social media interactions on this topic ranging from ‘don’t make it at home, you will die’ to ‘only this very specific combo of ingredients works’. The reality sits somewhere in between as is so often the case, most people offering up advice whether qualified or not has something of value to share, often based on fear, frustration or desire to help.  We do well to pay attention to those emotional triggers as staying connected and compassionate to others may well keep us as safe as any hand sanitiser formula you care to come up with.  Maybe ‘made with love’ is an ingredient we need more of in this world, in spite of how much those words irk me when I see them on an ingredient label!  I digress…

So can you make your own?

Yes, yes you can but you can’t make any old shit up and think you are onto a winner so don’t get too excited, this gets quite complicated.

Unlike sunscreens, hand sanitising products are a relatively low-risk product to make at home as long as some simple qualifiers are adhered to.

Sunscreen manufacture requires a lot of formulating skill, preferably some high-tech mixing equipment (a homogeniser rather than just a whisk or hand blender), knowledge of how to select exactly the right ingredients/ ingredient combo and expensive post-formulating testing for micro, physical and chemical stability and efficacy.  Hand Sanitisers require you to put about three to five basic ingredients together in a range of evidence-based proportions using a clean but not high-tech mixer before packing off in a way that avoids evaporation.  Not so hard hey?

The problems with making hand sanitisers come in several stages, the first one being ignorance.

Ignorance can be overcome quite easily in the case of hand sanitiser formulation. One only has to google the World Health Organisation’s guidelines on hand hygiene in health care to be gifted two formula options, both of which sit within a 262 page report which highlights nearly everything you need to know to at least be in the right ball-park, especially if you only want to make a spray (as the two formulations are spray based rather than gels).  Here is a link to the report. 

For those who are too busy looking awesome on Instagram to read such a boringly long report the report states that both ethanol and isopropanol are useful as the main actives due to their ability to denature proteins. Both have validated virucidal activity and look to be helpful in our current climate although neither kill all viruses and neither should be relied upon as the sole hand hygiene active – soap and water are still required to clean off visible dirt before any sanitising step happens.  Of these two alcohols, ethanol is seen as the best option due to its broader efficacy, lower toxicity and higher aesthetic tolerance among the public (less smelly).  On that note, never underestimate a products aesthetics influence on performance – they like the smell, they wear the product.

The two WHO formulations (that were published in 2009, so a long time ago now) also contain glycerin (1.45%) as a humectant to protect the hands plus a little peroxide as a further disinfectant (0.125%).

Given that alcohol works by denaturing proteins (the skin is a protein), the presence of a humectant/ skin protector in a sanitising product is very important.  Since the publication of the WHO document, further studies have been carried out  to establish an optimal glycerin concentration for this type of product.  This is important as the presence of a humectant has been found to reduce the efficacy of the sanitiser when the humectancy level is sub-optimal.  What percentage constitutes sub-optimal is likely to be dependent on both the humectant chosen and the environment/ climate in which it is being deployed.  This study was undertaken in a tropical environment, please don’t assume the same glycerin level would be applicable in very dry or more temperate climates, I’m trying to find data but haven’t found any more as yet.

As a cosmetic scientist rather than a virologist, pharmacist or medical doctor the lane that I’m wise to stay in sits around the aesthetics/ skin conditioning part of this equation and as such, the humectant’s role in this product is of great interest to me.  It wouldn’t matter how great or effective a hand sanitiser performs in lab testing or in single-use studies if the continued / real-life use of the product was intolerably painful for the public.  As someone with severely eczema affected skin I know that once my barrier is broken I’m both more vulnerable to infection myself and more likely to pass on infections to others. If a hand sanitiser can’t maintain my skins barrier function and integrity I would either use it very infrequently or not at all – low to zero efficacy!

The peroxide part of the WHO equation has not been as broadly adopted in the world of commercial hand sanitising as the layperson might expect after reading the attached study.  One key reason for that is the practical difficulty in stabilising peroxide solutions in consumer products, another may be the cost vs risk equation (risk being of product failure, bottle blowing etc).  So, commercially brands have tended to stick to alcohol, water, glycerin and a thickener plus (on occasions) a fragrance, to get the job done.


Alcohol percentage.

Most people I meet and talk to have trouble with the type of math we do in cosmetic science.  It is likely that this is what is causing at least some of the confusion over how much alcohol is needed in a hand sanitiser.

Alcohol is a family of ingredients and here we are referring either to Ethanol or Isopropanol.  Both have specific gravities less than 1 which mean they are lighter than water which has a specific gravity of 1 exactly, that means it weighs the same as it takes up in volume. 1ml = 1g.  Isopropanol has a specific gravity of 0.786 and Ethanol a SG of 0.7893 so very similar with ethanol being that little bit heavier.

The reason I mention this is because most recipes talk of a percentage to add but confusion can come about when comparing efficacy data and scientific reports on alcohol concentration in products due to the variety of ways we can describe concentration.

Some will refer to the alcohol concentration using weight for weight units, some weight per volume and some volume per volume.

I found this which, while it uses US based units, is quite helpful in working through an example of how this can change things.

In that example a 67% W/W solution works out as a 64% W/Vol solution and a 75% Vol for Vol solution for a simple, binary (two option) product. That changes when you add more things to the formula and create a new specific gravity.

The above figures are about the figures you get when you take 95% Perfumery alcohol (supplied as a W/W percent activity) and add 70g of that to 30g of water – this is about the concentration that I’ve most typically been referring to as in ‘the ball park’ when talking to clients.

The WHO formulations used V/V as their descriptor for alcohol concentration and talk about anything from 60-80% V/V alcohol as being within the active range which means the typical dilution that I’ve been talking about should be fine in terms of alcohol concentration.


Bringing it all together as a formula.

So once you understand how much alcohol you need and you have thought about protecting the hands with a little humectant, the next thing is getting that into a form that makes the product more effective, often that means turning it into a gel as gels tend to be more spreadable and stick-on-able than a simple spray and are often faster drying than a cream.

Not all gelling polymers are stable with alcohol solutions, especially when the alcohol is at a very high level such as found in these sanitisers.  What you might find if you start experimenting is that the gel polymer thickener becomes thinner as the alcohol is added and if the gel loses enough viscosity (due to the change in solvent polarity) the gelling agent becomes pretty useless.  Various acrylate based polymers can withstand alcohol at the levels discussed here and that’s why you often find carbomer or acrylic acid copolymer thickener type INCI names on sanitising gel solutions.  When using carbomers that need a neutralisation step, the best option is to use polyvalent alkali to do that rather than a monovalent ion.  The reason for that is the multi-valent alkali can form more cross-links than the monovalent one.  So, that’s why you tend to see Triethanolamine salts used instead of Sodium Hydroxide where this neutralisation step is required.

For those looking for natural options, the temptation may be to look at xanthan gum as that’s cheap and widely available.  Xanthan gum does have some alcohol tolerance and studies have found some compatibility up to 40% alcohol concentration but above that, the polymer can precipitate out thus destabilising the product and leaving your hand sanitiser in two phases – a thickened gel phase and a watery phase that is blocked under a jelly-like plug.  There are lots of other natural gum agents out there but finding one that can tolerate such high levels of alcohol has turned out to be impossible so far (although I’ve probably not exhausted all scientific papers) with the highest figures I’ve seen being that for xanthan. Some cellulose gums (Tic Gum is a trade name with some data on that) can be used to stabilise alcoholic spirits (typically at 20-40% alcohol concentration) and Sclerotium Gum (Amigum/ Gel) is promoted as being alcohol stable but for that, it’s viscosity dramatically reduces after 15% alcohol so again, not enough for this purpose.

As well as thickness, these ingredients bring the right rheology to the product, rheology being flow.  The acrylate based polymers we typically use in these formulations have a short flow so rather than roll up and ping back they easily break and spread across a surface. Because acrylates have a yield value of strength to them, they also avoid dripping off which together means your thickener adds spreadability and adhesion to the formula, both really important.


What about essential oils?

Essential oils are often added to hand sanitisers to make them more pleasant to use, remind us to use them or with a view to improving their efficacy (bug killing) or skin benefits (soothing, antioxidant etc).  Whether essential oils at the level added into these formulations add any measurable anti-microbial benefit is something I don’t have information on but as long as they do no harm and don’t change the alcohol activity in a negative way I can’t see a problem with them and can actually see some benefits (again, aesthetics matter).


Alcohol solutions of this type are generally self preserving but there could be exceptions to that depending on how you made the gel, how you pack it, what shelf life you are selling it with,  what other ingredients you add.  In general though, you won’t see extra preservatives added necessarily but some brands will add extra anti-microbial for both product protection (where needed) and efficacy (where there is an additional benefit).


Claims and the law.

So this article has crossed the cosmetic line in mentioning sanitisation, virus killing and other non-cosmetic things.  In Australia, hand sanitisers are cosmetic products as long as they don’t make specific micro claims and do not mention viruses. As soon as that line is breached you are in trouble. In other countries, the laws may be stricter and you may not be able to sell hand sanitisers at all so do be careful if you are thinking of doing so.  Check and comply with the law.


Other risks involved in alcohol sanitiser production. 

Alcohol is flammable so if we are going to end up with a situation where more homes have alcohol or high alcohol products around, especially in a kitchen, there could be an increase in fire hazard.  Taking care during manufacture, packaging and storage is very important.

Another issue with alcohol is its danger of incidental ingestion. The alcohol we buy for cosmetic purposes is high strength (95% typically) and denatured so it is not designed for ingestion. That said, kids can get into it and when it comes to adverse health effects of both hand sanitiser solutions when made and ingredients in their neat state it’s this exposure that is most common.  Keep the alcohol in a safe place, away from children and places where people may accidentally pick it up and drink it.


What about this, will frequent use of high strength hand sanitiser get me drunk or arrested for drink driving?

In short no.

The WHO report contains references to a number of studies that have looked into blood alcohol levels after extensive use of hand sanitisers containing up to 95% alcohol.  The worst case scenario study where 95% alcohol was used frequently did not result in a blood alcohol reading that was deemed insignificant at 2mg per 100ml blood.  I’m not sure of the detection limits of Australian police breath testers but the limits for full licensed drivers here in NSW range between 20 mg per 100ml blood and 50mg per 100ml blood so that’s at least ten times higher than that worst-case scenario figure.  I think you’d be pretty unlucky to get into trouble or get drunk from using this type of product but some people have tried using hand sanitiser as an excuse!

Do keep in mind though that while we tend to focus on the dangers of chemical exposure through the skin, as alcohol forms vapours, there is a risk of exposure through the mouth (of the vapour, of course drinking it is an issue as mentioned above).  Again, both routes are thought to be very low risk but avoid adding to your risk by applying your hand sanitiser in a well ventilated room.

Anything else you should know?

I don’t think so at this point but there may be something I’ve missed.  Generally your best (and probably cheapest) bet is to purchase a ready-made product where you can but if supply dries up and you’re still able to buy all of the ingredients you shouldn’t be made to feel ashamed at having a go at making your own just as long as you are sensible and understand what you are doing.  If you have any doubt about your ability to create a safe and effective formula (and don’t forget, you would be legally obliged to have test data on your formula if selling it) then don’t do it, but if you are confident and especially if you are making it for yourself then I don’t see why you can’t give it a go.

The good thing about alcohol as a sanitising solution is that it doesn’t add to the development of resistant microorganisms such as MRSA etc like other biocidal chemistry can. That’s because it’s just physically attacking the virus coating rather than poisoning it or other microbes.  The worst thing that can happen is that you make something with little to no extra efficacy and therefore, waste your money and time.  If you are relying on this product due to chronic health issues, I’d suggest it’s not worth risking that, if it’s just an extra safety step for you and your family I’d again say ‘why not’.

The bottom line.

The most important step with regards to hand hygiene is in the washing with soap and water and then the adequate drying (wet hands are an issue, we haven’t mentioned that yet but here it is!). Once your hands are washed, hand sanitiser can help as an extra step and can be a useful top-up where wet washing is not an option.   Relying on these products to save you is not wise but using them as a reminder of the seriousness of the pandemic situation, as a step that draws your attention to hand hygiene, as a procedure that potentially increases your cleanliness and as something that helps you feel more in control will be helpful.

Thanks and sorry it was a long one. It’s been a while between posts (again)…




One Comment leave one →
  1. March 16, 2020 3:36 am

    Thank you for this thoughtful and timely post!

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