In today’s formulation we’re harnessing the skincare powerhouse that is salicylic acid with a simple formulation featuring a low-but-effective concentration of our star ingredient. Salicylic acid is commonly used in products for blemish-prone skin and has all kinds of fabulous skincare benefits, from brightening the complexion to cleansing pores. This formulation works out to about $0.35USD/oz (or $1.20USD/100g), making it a fraction of the cost of even the least expensive BHA products on the market right now. Let’s dive in!

Easy 2% Salicylic Acid Solution

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The key ingredients

The star

Our star ingredient is salicylic acid, also known as BHA (beta hydroxy acid). We’re using it at 2%, which is the maximum allowable level for cosmetics. Salicylic acid is a fabulous active ingredient. It’s oil soluble, unlike its AHA cousins like lactic and glycolic acids, which means salicylic acid is much better at getting down into pores to dissolve oil and debris and keep skin fresh and clean. Salicylic acid calms distressed skin, helps the complexion appear even and bright, and may help reduce the appearance of fine lines and wrinkles. Booyah!

The solvent

Salicylic acid isn’t terribly soluble in most things, and the ingredients it is somewhat soluble in still aren’t super effective solvents. At 3–6%Propylene glycol/ Propanediol 1,3 is one of the more effective solvents, meaning that straight propylene glycol or propanediol 1,3 can dissolve 3–6% salicylic acid. To make a 2% solution the formulation ends up needing to contain approximately 32–65% propylene glycol or propanediol 1,3 in order to dissolve the salicylic acid. I’ve gone with a number that assumes the solubility of salicylic acid at about 4.25%; the lower end of the range, but still giving us a bit of a margin of error. It worked, and I liked the feel of the final formulation, so I didn’t see the need to test lower concentrations of solvent. You certainly could if you wanted to find the absolute minimum solvent concentration, though 😊

Soothing Actives

A small amount of each panthenol (Vitamin B5) and allantoin help reduce irritation potential. You could use a different active or extract if desired; Paula’s Choice uses a green tea extract in their 2% BHA Liquid Exfoliant, and The Ordinary’s 2% Salicylic Acid solution includes some Saccharide Isomerate for a moisturizing boost. Remember that the pH of this formulation is pretty low, so whatever you choose needs to be relatively happy with a pH around 4.

Preservative

I’ve chosen phenoxyethanol to preserve this formulation. It isn’t highly water soluble, but it is soluble in propylene glycol, so we won’t have any incorporation challenges.

You could definitely use something else instead, keeping in mind that it’ll need to be effective at a pH around 4. This is a pretty easy-to-preserve formulation thanks to the high concentration of propylene glycol and the low pH.

pH adjustment

Without any pH adjustment this formulation has a pH just shy of 2, which is far too acidic for our skin. So, we’ll use a strong base to raise the pH of the formulation to a skin-safe level. A NaOH (lye) solution is industry standard; the one I’m using is a 10% solution.

We’re aiming for a pH around 4 for this formulation. Unlike alpha hydroxy acids like lactic acid, the performance of salicylic acid is not pH dependent. This study found that a salicylic acid solution with a pH of 6.5 was still effective while being less irritating than a comparable solution with a pH of 3.12, so if you have quite sensitive skin you might benefit from raising the pH to around 5, or even higher.

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A bit about our sponsor

A big thank you to Essential Wholesale for sponsoring this formulation! Essential Wholesale is a premium ingredient supplier located in the Pacific Northwest of the USA. They’ve been in business for over 20 years and sell both high quality ingredients and finished formulations, all of which are cruelty free. They also offer contract manufacturing if you’re looking to outsource your production. I visited Essential Wholesale back in 2018 and have been a fan of theirs ever since!

Save 5% on all the ingredients in this formulation (and everything else!) at Essential Wholesale & Labs with code HUMBLEBEE

Relevant links & further reading

Easy 2% BHA Solution

2g | 2% salicylic acid powder
45g | 45% propylene glycol

45.8g | 45.8% distilled water
0.2g | 0.2% allantoin
1g | 1% panthenol

1g | 1% phenoxyethanol

5g | 5% 10% NaOH solution

Weigh the salicylic acid and propylene glycol in a beaker. Stir to combine, cover, and leave to dissolve. This will take about an hour.

In a second beaker, combine the distilled water, panthenol, and allantoin. Stir to combine, cover, and leave to dissolve.

When the salicylic acid has dissolved, stir the water and salicylic acid mixtures together. Add the phenoxyethanol and NaOH solution. Stir to combine.

Once the mixture is uniform, it’s time to test and adjust the pH.

To test and adjust the pH: create a 10% dilution by weighing 2g product and 18g distilled water into a small bowl or beaker and whisk to combine (wondering why we create a dilution to check the pH?). Check the pH with your pH meter. Depending on the shape of your bowl/beaker you may need to tilt it in order to fully submerge the sensor on your pH meter. We are aiming for a pH of 3.7–3.9; you will almost certainly need to raise the pH using more 10% NaOH solution, testing as you go. I have created a supplementary Patron exclusive video for this formulation that includes a step-by-step demonstration of making the 10% NaOH solution, testing pH, and adjusting it; it’s available at $10 and up tiers. You can also read this article from Skin Chakra to learn more about pH adjusting.

When the pH of the solution is around 4, package it up! Before you select a bottle, check the side of the beaker to see how much product you have left after pH testing and adjusting; you can end up losing a lot to testing as you get a feel for how much different amounts of the NaOH solution raise the pH. I divided my batch (I ended up with roughly as much as I started with) between three 30mL (1fl oz) clear bullet bottles fitted with orifice reducers (the orifice reducer means you can shake out the solution a couple drops at a time). A dropper-top bottle would also work well.

If you are new to including salicylic acid in your skincare routine, please introduce this product to your routine slowly. I’d start with using a few drops of this serum ~3x a week, gradually working up to daily use. Avoid the eye area! I generally use this serum along with other watery serum type products, before any creams or oil serums. Pay attention to your skin, looking for signs of irritation, and discontinue/reduce use if your skin isn’t happy.

Shelf Life & Storage

Because this solution contains water, you must include a broad-spectrum preservative to ward off microbial growth. This is non-optional. With good manufacturing practice and proper preservation, this formulation should last at least a year. Even with a preservative, this project may eventually spoil as our kitchens are not sterile laboratories, so in the event you notice any change in colour, scent, or texture, chuck it out and make a fresh batch.

Substitutions

As always, be aware that making substitutions will change the final product. While these swaps won’t break the formulation, you will get a different final product than I did.

  • As I’ve provided this formulation in percentages as well as grams you can easily calculate it to any size using a simple spreadsheet as I’ve explained in this post. As written in grams, this formulation will make 100g.
  • To learn more about the ingredients used in this formulation, including why they’re included and what you can substitute them with, please visit the Humblebee & Me Encyclopedia. It doesn’t have everything in it yet, but there’s lots of good information there! If I have not given a specific substitution suggestion in this list please look up the ingredient in the encyclopedia before asking.
  • Don’t substitute the salicylic acid; it’s the star ingredient!
  • You can use propanediol 1,3 instead of propylene glycol.
    • This formulation needs an adequate solvent for the salicylic acid. That is what the propylene glycol is.
    • You cannot use glycerin or octyldodecanol.
    • High proof alcohol can work as an alternative solvent, but it’s a very different ingredient than propanediol 1,3/ propylene glycol.
  • You don’t need to use panthenol (Vitamin B5) and/or allantoin. You can replace either or both of them with more distilled water. You could also use a different skin-soothing active or botanical extract.
  • If you’re like to use a different preservative, please review this FAQ and this chart.
  • I don’t recommend using a different ingredient to raise the pH.
    • If you have to use something else, baking soda could work, but it’s far less potent than NaOH so you’ll need a lot more. Read this for more details.
  • If you don’t want to worry about pH, make this anhydrous formulation instead: Beginner-Friendly Salicylic Acid + Squalane Serum.

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Gifting Disclosure

The ingredients used in this formulation were gifted by Essential Wholesale.
Links to Amazon are affiliate links.