Hand Sanitizer Doesn’t Expire, So Why Do They Have Expiration Dates?

Dur­ing the H1N1 pan­demic at the end of 2009, the Province of Ontario was dis­trib­ut­ing kits of sup­plies to health­care pro­fes­sion­als in the field. Many of the kits being dis­trib­uted con­tained hand san­i­tizer that was, tech­ni­cally, expired. We received calls from doc­tors’ offices and med­ical insti­tu­tions about the expired hand san­i­tizer ask­ing us if it’s safe to use. As I sit here at my desk look­ing at a bot­tle of hand san­i­tizer that expired in April 2010, I think it’s time to share with you why hand san­i­tizer has an expi­ra­tion date but doesn’t actu­ally expire. It’s safe to use well past its expi­ra­tion date.

One of my col­leagues calls this a marketer’s dream, but there is some valid­ity behind the use of an expi­ra­tion date. I’m look­ing at a bot­tle of Purell hand san­tizer and the label tells me it con­tains 62% ethyl alco­hol with the other 38% made up of water, glyc­erin, iso­propyl myris­tate, propy­lene gly­col, toco­pheryl acetate, aminomethyl propanol, car­bomer and fra­grance. It’s really the ethyl alco­hol that kills the bac­te­ria by lit­er­ally boil­ing them to death. Alco­hol vapor­izes (boils) at a much lower tem­per­a­ture than water, but is entirely water sol­u­ble. There­fore, the bac­te­ria absorb the alco­hol when you rub your hands with the stuff and then are lit­er­ally exploded from within as the alco­hol they’ve absorbed boils away. In any case, it’s the alco­hol that does the trick — the rest of the ingre­di­ents are there to make the san­i­tizer into a gel that feels okay and smells okay to the user.

The bot­tles we use to pack­age, trans­port, and dis­pense the san­i­tizer are not air­tight. There is some leak­age going on whether at the seams where the caps/pumps are screwed on, or even right through the plas­tic itself. Alco­hol evap­o­rates right out of the bot­tle over time. That is the key to the expi­ra­tion date.

At some point, the san­i­tizer in the bot­tle will no longer com­prise 62% or more of the con­tents. Enough will have evap­o­rated to lower the con­tent to some­thing lower — say, 61.9%. At that point, tech­ni­cally speak­ing, the bot­tle has expired. The nature of the con­tents, par­tic­u­larly the active ingre­di­ent, no longer reflects what it is labelled as being. Is the san­i­tizer still usable? Sure. Is it still effec­tive? You bet. But many peo­ple, even health­care pro­fes­sion­als, don’t know why there’s an expi­ra­tion date. They just know that when they see that something’s expired, it’s time to throw it out and buy a replacement.

Bam! That’s great for busi­ness! The prod­uct is still good, but your cus­tomers and con­sumers are throw­ing it out and buy­ing more from you! Given the fan­tas­tic mar­gins on what is essen­tially a dirt-cheap prod­uct (much like soft drinks, I might add), this is a won­der­ful sit­u­a­tion for the manufacturers.

But is it a total sham? Not entirely. At some point, with enough evap­o­ra­tion, yes the san­i­tizer will be inef­fec­tive. Given enough time, all of the alco­hol will even­tu­ally evap­o­rate out of the bot­tle. But that will take a long, long time — not the span of 3–5 years as indi­cated by the expi­ra­tion dates. It’s true that there are guide­lines rec­om­mend­ing that every­one buy and use hand san­i­tizer with >60% alco­hol con­tent — and you can buy them as high as 90% alco­hol — but if you know you have expired san­i­tizer you can just use more of it to ensure you’re using enough alco­hol to do the trick.

Hand san­i­tizer does not expire, at least not within the times­pans indi­cated by the expi­ra­tion dates on the bot­tle. You can over­shoot it by a few years and still have a safe, usable prod­uct. But if you’ve gone over by, say, 5 years or more… by that point your prod­uct is 10 years old and yeah, it is time to throw it out and get a new one. By that point, the san­i­tizer will most likely still be safe to use, but it might smell a bit funky because the fra­grance has started to change — and I’m not sure how nice your bot­tle is going to be on the out­side by then either! Your hands prob­a­bly weren’t absolutely clean when you grabbed the bot­tle all those times over the years, right?

On a final note, alco­hol evap­o­ra­tion isn’t just lim­ited to hand san­i­tizer. It also hap­pens with wine and liquor pro­duc­tion. A col­league who used to work for a dis­tillery tells me that ware­houses full of whiskey aging in wood bar­rels are full of alco­hol vapors. If you walk into the ware­house where the bar­rels are sit­ting and the whiskey is aging, make sure you keep the doors open or you will be drunk within 20 min­utes from the alco­hol vapors being absorbed into your blood­stream. That’s entirely off-topic, but I had to share that!

ADDENDUM 2013-01-06

Ah! Charles posted a com­ment not­ing that there’s an addi­tional fac­tor that I didn’t address in the orig­i­nal write-up. To be more accu­rate, it just didn’t occur to me. It’s a mat­ter of con­cen­tra­tion. Below some thresh­old value, the alco­hol in expired san­i­tizer will no longer be con­cen­trated enough to kill the bac­te­ria. It’d be like try­ing to kill tigers by shoot­ing nerf balls at them. I’ll try to find out what the rel­e­vant thresh­old con­cen­tra­tions are for the key bac­te­ria that we’re try­ing to kill.

ADDENDUM 2013-01-08

New update posted! The expi­ra­tion date isn’t hard-and-fast, but you do want to pay atten­tion to it in rela­tion to the printed alco­hol con­cen­tra­tion.

10 responses

  1. Read­ing this arti­cle was inter­est­ing. The last para­graph men­tioned walk­ing through dis­tillery and absorb­ing vapors through the skin.
    My ques­tion is what about health care pro­fes­sion­als who are always using san­i­tiz­ers, at the end of the day how much has been absorbed?

    Just curi­ous
    Thank you

  2. Ah. The last para­graph was sim­ply stat­ing the alco­hol evap­o­rat­ing has other effects in other cir­cum­stances, not that it gets absorbed through the hands when using alcohol-based san­i­tizer. With the dis­tillery ware­house work­ers, they are absorb­ing the alco­hol through their lungs. The gas exchange tis­sues in the lungs are much much thin­ner than the skin — and indeed are made to be per­me­able whereas the skin is sup­posed to be a bar­rier with the envi­ron­ment. I don’t have hard stats handy, but alco­hol absorp­tion through the skin is extremely low to none.

    We’ve never had any con­cerns with alco­hol absorp­tion through the skin with alco­hol san­i­tiz­ers. We have, how­ever, had ques­tions about alco­holics eat­ing the foam or gel, but again that’s a dif­fer­ent mat­ter altogether!

  3. Hi, I recently tried to kill a ton of bac­te­ria with hand san­i­tizer that expired in 2012 (2 1/2 years ago). It didn’t work at all! I’m now try­ing to repeat it with fresh san­i­tizer. I assume the results will be dra­mat­i­cally bet­ter. Hope this helps!

  4. Brent, were you doing this in a lab? :) I think you’ll find the fresh san­i­tizer to be quite effec­tive. Alco­hol that’s at a strong enough con­cen­tra­tion is very effec­tive at killing the lit­tle buggers.

  5. Inter­est­ing. I have a bot­tle of Germ-X with an expi­ra­tion date of 08/09, so I’ll be throw­ing this one out. Will try to sub­scribe to your newsletter.

  6. Yeah, I think the alco­hol con­tent on that bot­tle of Germ-X is going to be well below the 60% mark by now :)

  7. Thanks for the arti­cle!! Really use­ful as I was about to throw my expired hand san­i­tizer away..

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