Are Preservatives Necessary in Solid Conditioners and Shampoo Bars? A Test Begins

Today, we're going to take a look at a little test I was inspired to undertake late last year because of the seemingly endless amount of confusion about whether or not preservatives are necessary in solid conditioner and shampoo bars.

In my own formulas, preservatives are not required.

If you're thinking I make some kind of amazing magical formulas that no one else on the planet has ever thought of before and probably ever will again, you would be incorrect.

(sorry if I just burst a bubble)

I would go so far as to maintain that anyone making conditioner and shampoo bars in a similar way to the way I make mine, will not need to add preservatives.

Does this mean people who don't add preservatives to their shampoo and conditioner bars are dousing themselves with bacteria and nasties?

Not at all.

Let's take a closer look.

Constant Exposure to Water is Asking for Trouble

Now, I realize full well both shampoo bars and solid conditioner bars are used in the shower and bath and repeatedly exposed to water, wetness, moisture, humidity, and everything else bacteria loves with a passion.

However, there are a couple of things worth observing.

For one thing, these are solid, hard (pressed) and (for the most part) anhydrous products.

Even a solid product that is constantly exposed to moisture and wetness has a limited amount of exposure area. Even if it gets thoroughly wet (which it does in a shower), it is only wet on the surface of the product.

Soap vs SYNDET bars

This is not unlike the way a bar of soap is exposed to water during use. And although it is somewhat comparable, soap is still different from a SYNDET (SYNthetic DETergent) shampoo bar and solid conditioner bar in that the pH of a bar of soap is naturally much higher – making it far less susceptible to pathogens. Have you ever heard of anyone adding preservatives to a bar of soap? That's because it isn't necessary.

Even though they are (comparably) solid, SYNDET shampoo bars and conditioner bars generally have a lower, more skin and scalp friendly pH which is unfortunately also a more 'pathogen-friendly pH' .

And if it sounds like I just made an argument against preservative free, the fact remains that
exposure to water is still limited in an unpreserved solid bar.

After each use, it DRIES again.

No water = no pathogen-friendly environment.

OK. So it works if you are careful to dry the product /allow the product to air dry after every use.

Of course, not everyone does that.

So let's say an unpreserved shampoo / conditioner bar is living in a place where it is constantly wet and allowed to stay wet to the point where it gets all smooshy and gross. That might just be the most bacteria-and-pathogen-inviting kind of situation of all.

Putting Preservative Free to the Test

I decided to put one of my own unpreserved solid conditioner bars through the wringer, and if you check back for the next post, I'll walk you through the entire process.

Teensy spoiler alert: the test is still ongoing.

Do Tell

Do you add preservatives to your solid conditioner and shampoo bars? Please share in a comment below.

Want to make your own preservative free solid shampoo? This e-book contains preservative free formulas and something for every hair type


Wendy W said…
I have to admit I am one of those "no preservative" folks - and have never had a problem with my bars. However, mine do dry out between uses.
Jackie Coup said…
I make and sell solid syndet shampoo bars and conditioner bars. I add a preservative (minimum amount) to mine. Who knows how my customers will treat them - they may put them in a storage tin still wet, get on a plane and travel to a hot country then sit on a hot bus for a while, go backpacking, camping and hiking. Very unlikely in this scenario they would take the time to dry out their shampoo bars. ;-(
LisaLise said…
@Wendy W - Nice to hear! Mine have always dried out between uses as well, but I figured it was time to test limits :)

@Jackie Coup - I understand where you're coming from. I wonder if the next post (where the results of this bar after 50 days is revealed) will cause you to reconsider although the idea of letting a bar go all smooshy in an aluminum tin intrigues me... I might have to test this! :)
Sira said…
I just made 3 bars and completely forgot to add my eco preservative. So I guess time will tell! I don’t suppose there’s a way of adding it now while the bars are semi solid?
LisaLise said…
Hi Sira - It is not possible to add a preservative to these after the fact and be sure it is properly and completely distributed throughout. I'd start over if you want to include a preservative.
Braidedlady said…
I'm having trouble finding the results from this test. I'd be interested to know how it went. Do you have a link for it? I searched the site but can't seem to find it.
LisaLise said…
Hi Braidedlady -- check here :)