What is an alum stone and how do you use it?

Crystal deodorants seem like utter magic at first glance. A block of salt that can be used as deodorant, aftershave and a styptic? We, like many of you, were huge skeptics before we joined the alum stone club.

You might have seen the Crystal brand deodorant in drug stores, in a plastic applicator just like regular roll-on deodorants. It's touted as all natural and has recently come back into popularity, but a lot of people have never had success with it. Well, not only did we find an alum stone that's completely unpackaged and will last you for years at a time, but we discovered the secret to making it effective! Here we share all our best tips and break down what an alum stone is actually made of and how it works.

What on earth is an alum stone?

Alum stones are a mineral salt in crystal form, made of a single ingredient: potassium alum. This is not the same chemical compound as the aluminum which is found in most conventional deodorants. Potassium alum has antimicrobial properties (which is a big part of why they work), and it has been used since antiquity. Ancient Egyptians used it as a dye, as a mordant in textiles and for tanning. Beginning in medieval times, it was used in medicine as a styptic for minor wounds and cuts. It is still widely used in water treatment, medicine, cosmetics, and even in food (in baking soda and pickling). You can find it at pharmacies as a styptic pencil for first aid, at barbershops as an aftershave, and in cosmetics as an astringent. It has been used as a deodorant for a long time as well, and ours has a smooth rounded shape that's easy to hold and easy to apply.

Alum stone crystal deodorant

How does it work?

Unlike other deodorants, alum stones don't cover up body odor with fragrances or perfumes. Instead, the salt works to stop odor-producing bacteria from ever forming in the first place. As a mineral salt, it is naturally antimicrobial and antiseptic, which allows it to fight bacteria. Think of it as a layer of salt that sits on the surface of your skin and keeps odor at bay. It leaves zero scent on the skin and it's hypoallergenic which is great for sensitive skin. Plus, it's a clear salt, so there's no white streaks!

As an aftershave, it tones and firms the skin and it also stops any bleeding from nicks or cuts. It is a styptic, meaning it tightens tissue and helps blood to clot, so you can use it on your face, legs, or anywhere else you have a cut. It's popular for use after shaving, but we also like to keep one in our first aid kit to treat small cuts and abrasions as well.

It is astringent and drying, so you can even use it on blemishes to heal problem areas and draw out oils and impurities.

Is it safe?

Yes, alum stones are a safe and effective natural deodorant. It is important to note that they are made of potassium alum which is a different chemical compound than the aluminum found in conventional deodorants, and they do not possess the same health risks. Regular antiperspirant deodorants usually contain either Aluminum Chloride, Chlorohydrate or Zirconium, all of which have health concerns. Potassium alum on the other hand is a mineral salt with a large molecular structure that sits on the surface of your skin rather than being absorbed. It is not a heavy metal and has not been linked to breast cancer or Alzheimers.

Alum stones differ from antiperspirants in that they are not thought to disrupt the microbiome of your skin. Also, the aluminum found in conventional deodorants is thought to be an endocrine disruptor which causes all kinds of hormonal problems and health risks. Yet another reason you might want to make the switch to a crystal deodorant.

We loved this Mind Body Green article on how crystal deodorants work and what dermatologists had to say. It links to some helpful research articles, too. The Environmental Working Group (EWG) deems it safe as well, which gives us peace of mind.

The beauty of a crystal deodorant is that it's free from all the additives and ingredients that usually cause irritation, like parabens, phthalates, artificial fragrances and dyes. It is safe for sensitive skin and free of toxins.

Zero waste alum stone deodorant crystal

How do you use an alum stone?

You can use an alum stone as a deodorant, aftershave or astringent. Be sure to dry it off between uses and store it on a tray (we like using an upturned jar lid!) to keep it long-lasting.

Here's our best tips and tricks for each use.


To apply as deodorant, simply wet the top of the alum stone and rub it onto your skin as you would any deodorant. Smooth it onto your underarm area until most of the water is absorbed, to create an invisible salt layer. 

The secret to making the crystal deodorant effective is to make sure you're applying to clean skin! Before you apply, make sure you've either showered, shaved, or simply cleansed the underarm area with a little soap and/or hot water. Any of these will work, but the idea is to make sure you have no odor to begin with. The alum stone won't hide odor that's already there, but it can prevent any from appearing on clean skin! If you find it easier, you can also apply your alum stone the night before and in our experience it lasts through to the next evening.

You may experience a detox period if you're switching from traditional deodorant. Give your body a few weeks to adjust to the difference and you should see it start to work.

A lot of our customers say it makes their skin feel super silky and soft after use. An added benefit of its toning properties!

If you're still feeling skeptical, we totally get it. Check out our growing list of over twenty rave reviews.


Many people like to use the alum stone on their face after a shave because of its toning and astringent properties. It is also antiseptic, meaning it can help soothe any razor bumps, razor burn or redness. To use your alum stone as an aftershave, wet the top of the stone and apply to your skin directly after you shave. Rub the stone around until most of the moisture is absorbed.

If you want to apply an aftershave balm or facial moisturizer as well, splash some water on your face after using the alum stone and then follow it with your moisturizer or aftershave.

To use it to stop bleeding, wet the top and rub over the cut until it dries, and it should stop bleeding almost right away. It can sting a bit since it's a salt, but that means it's working.

You can also use this after a bikini wax or sugar wax because it calms the skin, protects against infection and should soothe any inflammation or bumps that can occur. It can have a light stinging because it is a salt, so try this with care. 


The alum stone mineral salt crystal can be a great spot treatment for oily complexions and acne prone skin. It's an astringent, which means you can use it to dry out problem areas or just tone and tighten your skin. Simply wet the top and apply to affected areas.

You can do this at night, or in the morning but do note that it can be drying on some skin types. Be careful to not over-use this treatment as it can dry out your skin or throw your natural oils out of balance. A couple of times a week should be fine.

How long does it last?

As a deodorant, each stone will last you for years! The idea is to rub it on your skin until most of the water is absorbed into the salt, so the more you apply the better. But I’ve had mine for a year and a half and it barely looks different at all. The top has definitely gotten flatter so I know it’s not magic... I’m going to guess five years but it totally depends. Bea Johnson says hers lasts about ten years! As an aftershave, it depends how often you use it but probably around the same.

You can use your stone until it’s too small to hold. After that it’s basically a small rock so you won’t want to try to compost it, but you can keep it as decorative or sand it down into a powder, add it to water and turn it into a deodorant spray!

The magic of crystal deodorant

The history of alum stones is absolutely fascinating, and there's so many ways to use them. As a crystal deodorant, they look stunning on your counter and one stone can last you for years! As an aftershave, they are multipurpose in that they tone the skin and stop bleeding. As an astringent, they can be used in skincare as a treatment for blemishes and acne. This mineral salt stone is quite versatile, and I for one am a convert. Try it for yourself and let us know what you think!