A little-known reason to use Alum after shaving

An alum block is a pretty standard item in a wet shaver’s collection, but it was one of the last things I added to mine.  I understood some of the benefits, but it never struck me as a critical tool.  I very rarely cut myself and I had some concerns about alum drying my skin.  I wasn’t sold on its benefits until I realized something interesting – the pH of alum can have some real benefits for a traditional wet shaver.

Traditional benefits of alum

Prior to purchasing an alum block I had read about its benefits.  One of the primary benefits is the astringent qualities of alum.  Astringents cause tissues to contract, which has the benefit of closing up any “weepers” – the tiny specks of blood left behind after a particularly harsh shave.  Alum also causes the skin to tighten up a bit.  It may all be in my mind, but I feel like my shave looks a little “closer” after using alum.

Alum also has some antiseptic qualities.  Research shows that alum has effective antibacterial properties, which can be helpful in shaving.  Shaving can give bacteria the opportunity to populate the nicks, cuts and pores in your face, which can lead to complexion problems.  This can be avoided with proper cleaning and sanitation, but using alum can be a good insurance policy.

There is value in the astringent and antiseptic qualities of alum, but they weren’t enough to make me buy a block.  That didn’t happen until I dipped a pH meter in a tub of shaving cream…

An aside…

Humor me for a minute while I go on a little tangent.  This has relevance, I promise.

I really like fermented food.  Sauerkraut, pickles, kimchi, kombucha…I think it is all delicious.  When I was younger it was the sour taste that I liked the most.  Then I came across a book that has become one of my favorites – Wild Fermentation by Sandor Ellix Katz.


I learned a few really interesting things.  First I learned that it is very easy to make fermented food at home (cabbage + salt + time = sauerkraut).  My basement almost always has something bubbling, whether its kombucha, pickles or sauerkraut.

Second I learned the health benefits of fermented foods.  Our bodies are supposed to have a ton of bacteria and our post-industrial habits are harming the good bacteria in our systems.  Our “helpful bacteria” make up an enormous part of our immune systems.

But the relevant insight for this post is the relationship between pH (acid vs base) and bacteria.  Fermentation was the first form of food preservation.  It works because “good bacteria” create acids (hence sourness) and bad bacteria generally don’t like the acidic environment.  So the good bacteria kill the e. coli and salmonella AND turn your boring cucumber into a kosher dill… I call that a win.

Soap is alkaline but your skin wants to be acidic

Here is the connection between sauerkraut and your skin – both use acidity to defend against bacterial intrusion.  Your skin’s acid mantle is a thin layer of oils and acids that keep your skin at a slightly acidic pH – around 5.5.  Bacteria that cause acne like a pH that is higher (more alkaline) so the acid mantle serves as a first line of defense against pimples forming.

I love using artisan natural soaps for shaving, but they have an alkaline pH – typically between 8 & 9.  Drugstore shaving creams also fall into the same pH range.  Unfortunately this means that the cream/soap is disrupting the natural state of your skin by making it more alkaline.  In theory, this can weaken your skins natural defense against bacterial infection and make your skin work overtime to restore its natural pH level.

Here’s where alum comes in…

Unlike soap, alum is acidic with a pH around 4.  Using alum after shaving can help to restore the skin to its natural pH, thereby restoring some of your skin’s natural defenses against infection.

These pH strips show the alum with a pH of 4 and the soap with a pH of 8.

The idea of using acidic toners to restore skin’s pH is nothing new.  Many people who use natural skin products will dilute acidic apple cider vinegar and apply it to their skin for many of the same reasons.  Alum will achieve similar results with the added astringent benefits (and less of the pickle smell).

Will all hell break loose if you don’t use alum?

After all this talk about disrupting your skin’s pH, the question remains – “will I turn into a bacterially-infected mess if I don’t use alum”?  The answer, of course, is no.  Wet shaving alone cleared up any issues I had with pimples and ingrown hairs – even before I started using alum.

But in the absence of any harm it makes sense to add alum to your regimen.  Our skin has a specific pH for a reason and it makes sense to help it stay that way.  I have not experienced any negative side effects from using alum, but I do enjoy the astringent and antiseptic qualities.

If nothing else, many of us enjoy the ritual of wet shaving as much as anything else.  Smoothing a cool block of alum over freshly-shaven skin is one more element of the ritual to look forward to every morning.

Which alum to buy?

Alum is a pretty simple one-ingredient product so there isn’t much need to obsess over which brand to buy.  I went with the low cost Gentleman Jon Alum Block.  It costs less than $8, lasts forever, and comes with a plastic case for storage.

Further reading

The purpose of this blog is to share how double-edge shaving can help men get better shaves and clearer skin.  Here are some additional posts you may find interesting:

Intro to Wet Shaving – A primer on how DE shaving helps give better shaves and clearer skin

Shaving Technique – A “how-to” guide for shaving with a safety razor

DE Shaving Cost Comparison – Analysis comparing the cost of DE shaving vs cartridge shaving (spoiler: DE razors are cheaper than dirt!)

Gear for Beginners – The low-cost tools that introduced me to DE shaving

Razor Aggressiveness Basics – An explanation of what makes a razor “mild” with recommendations for beginning DE shavers

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