Friday, February 26, 2010

Alpha-hydroxy acids

Alpha hydroxy acids or AHAs come in many forms, but we are probably most familiar with the glycolic (this lovely molecule), lactic, and citric acid versions of this water soluble carboxylic acid.

I'm sure you've read a million times how fantastic AHAs are for our skin, but how do they work? The official statement is they induce epidermal effects through corneoctye disadhesion, operating by disrupting the ionic bonds between the cells so they can slough off and expose newer and lovelier cells underneath the stratum corneum, or top layer of cells. They also work as an anti-oxidant and can relieve post sun redness. All of these things make fine lines and wrinkles appear less obvious, reduce redness and inflammation, and expose new, shiny skin to the world.

AHAs work by penetrating our skin through the stratum corneum to the stratum granulosum. It acts as an exfoliant on the top layer of our skin by disrupting the bonding between the cells and allowing them to slough off, revealing those new and lovely cells I spoke of earlier.

With salicylic acid or BHA, this sloughing off of the skin occurs at the stratum corneum layer: With AHA, this happens at the stratum granulosum level, with the cells being pushed up, as it were, to reveal new skin.

AHA is considered stronger than BHA as it works from the lower to the upper levels of our skin, but this can work against us if too much of the stratum corneum is exposed. This can increase transepidermal water loss, so you will want to add extra humectants and occlusion ingredients to any lotions including AHA. This can also lead to thinning of the stratum corneum, so you will want to make sure if you are using AHA products, you're keeping your skin well protected. Always use a sunscreen if you are using AHAs in your products because AHAs can make you sun sensitive (even if you're using it in night cream, as taking the moisturizer off won't necessarily make you less sun sensitive!). And note that because AHAs actually penetrate our skin, they will bring other active ingredients with them, which means some extracts and other wonderful things will be more effective as they penetrate the skin.

In one study, a lotion with 12% lactic acid increased the appearance of rough skin, increased exfoliation, and increased skin hydration by 33%. In another study, a 10% glycolic acid cream showed the exposed skin had a pinkish colouration with a shiny smooth surface.

How much AHA should you use? It is considered safe to use them at up to 10% of your product in the heated water phase, but you will need to adjust the pH with a buffer to a reasonable level if you're using that much! The ideal pH for AHA products is 3.5 to 4.0, so you really do want to make sure you have a pH meter or good pH testing strips nearby! I'd start low - say 1% or 2% - and work up if your skin doesn't mind it.

You can get AHAs in some extracts - anything containing rosmarinic acid like rosemary or comfrey or anything containing cinnamic acid like cucumber or shea butter - or you can buy AHA botanical water soluble extracts under names like Phytofruit or Multifruit. The combined extracts are easier to use - they tend to have better pH stability than raw extracts and some come with buffers built in - so just follow your supplier's instructions on when to include them.

As a note, if you are using something like rosemary as an AHA containing extract, you don't have to worry about balancing the pH. That's only for the raw ingredients like citric, lactic, or glycolic acids.

Try a toner or cleanser recipe to see how your skin likes the AHAs you are including - they're easier than lotions to make and you can use them almost immediately - and to see at what level you should include them. With the Phytofruit, for instance, I use 5% in a toner. If you are using the botanical extracts, try at 0.5% and see how your skin reacts.

Join me tomorrow for fun with horsetail extract - it contains some great natural AHAs!


Pam said...

Hi Susan,

Do you have a face cream recipe that includes the use of AHA?

Susan Barclay-Nichols said...

Hi Pam. No, as I've been waiting to get my pH meter so I could make sure the pH in the moisturizer was right. But you can use any moisturizer recipe on this blog or anywhere else, and add AHAs to the recipe (I offer some suggestions on how to do this in the post). I'll be experimenting in the near future with moisturizers with AHA and posting the results.

You can also add things like Multifruit or Phytofruit to your mixes - I have a post on Multifruit in the list of ingredients to the right of this!

Leman said...

Hi Susan,

I know this is an old post, I'd really appreciate if you can help me with this.. Can I add straight lactic acid or glycolic acid solutions (say 10% of 80% concentration lactic acid or 10% of 30% strength glycolic acid) in my cream/lotion/toner or facial wash instead of Phytofruit or Multifruit? I mean the type of acids that are used for peels?

Jen W said...

Hi Susan, I'm trying my hand at making a 7% Glycolic Acid serum. Last night I just diluted a 70% glycolic acid solution into a rose mist which is :

Rosa Damascena
(Rose) Flower Water, Citric
Acid, Sodium Hydroxymethylglycinate,
Citronellol, Eugenol.

Would hydrolyzed Silk proteins, Aloe Vera gel, or Hyaluronic acid be a good addition to this formulation?

Nedeia said...

Quite some useful info here :) I would love to play with AHAs as well, but I do not trust my pH testing papers, and I do not have any budget left for a pH meter :)

Catalina said...

I now use my AHA cream every day, under the eyes also,it is safe in pregnancy. Studies claim that AHA unblocks pores, keep them clear, so it helps in keeping acne under control.

Tawa said...

Hi Susan
how about Glycolic +Vitamin C ? How can I prevent the lotion from changing colour?

shannon said...

Hello! I am using the multifruit and had separating of clear liquid when I added it at 110 supplier told me to add it at a cooler phase of separated less this time but still had some separating
When using a multifruit. ..should I up the emulsifier and thickener?
I am currently using olive m 1000 at 5% and stearic acid at 2% (as I do for all my creams)
And or should I add the multifruit at a lower temp?

Susan Barclay-Nichols said...

Hi Shannon. In which type of product? Can you write up your exact recipe and process so we have an idea of what you've done?

Jennifer said...

Hi Susan, what buffers would you recommend for balancing the pH on ingredients like glycolic acid

Aesthete said...

I have the same question as Jennifer.

Anonymous said...

Hi Susan, can I mix my pure Coq10 powder with the 15% lactic acid lotion (Palmers cocoa butter lotion as a base). Waiting for your reply.

Anonymous said...

Yes, I would also like to know what buffers would you recommend for balancing the pH on ingredients like glycolic acic? and how do you go about doing so?

Thank you!

Susan Barclay-Nichols said...

Hi Lilo. You don't want to balance the pH of something with AHAs. You want the pH to be below 3.5 or so. Adding the AHAs to a product should get the pH that low. If you need it lower, you might want to look at the pH of the ingredients before adding the AHAs to see what you could change.

Izabela Gannon said...

Hi Susan, I would like to ask you what do you think about lactobionic acid with gluconolactone in toners or creams. I use them in my toner 6% of each plus 4% niacimine. do you have any thoughts or suggestions regarding of the usage of these ingredients?

Susan Barclay-Nichols said...

Hi Izabela! I've never tried these before, so I thought I'd offer a few links. This sounds very interesting, and I'm checking to see if anyone carries them! Where did you get yours?

Paula on these ingredients
It's all in my hands
The use of PHAs in photoaged skin

Kike Agadah said...

Hi susan can I add lactic acid to an anhydrous body butter recipe? Thanks

Susan Barclay-Nichols said...

Hi Kike! No, lactic acid is water soluble and anhydrous means "without water" or oil based.