The Science Behind My Favourite Skincare Acids

Hi, my name's Michelle, I'm a skincare nerd, and I'm an acid addict. Not that type of acid, I'm talking about skincare acids! Today I'm going to be talking about some of the best acid ingredients that you can find in skincare.

In chemistry an acid is a substance that donates H+, also called a proton. When I say the word "acid", you're probably thinking of bubbling test tubes, chemical burns, melting skin... But the right acid ingredients used in the right amounts can be really beneficial for your skin! In fact, your skin is naturally acidic thanks to the acids in your sweat and the fatty acids released from sebum, the oil that your skin naturally produces. The thin film of acidic goop on your skin is called the acid mantle. It's really important for keeping the right balance of bacteria and other microorganisms on your skin, so that the friendly microbes are happy and the harmful ones can't get too much traction. The pH of your skin should be somewhere between 4 and 6.

Let's get started on my favorite acids.

Alpha hydroxy acids or AHAs are ingredients that have a hydroxy or OH group on the carbon next to an acid or COOH group. Because of this positioning, AHAs have a special property: they can help your skin exfoliate. The top 10 to 20 layers of cells in your skin are dead. Around one new layer of cells is produced every day so one layer needs to come off or desquamate to keep your skin in equilibrium. If it doesn't come off properly you end up with dull flaky rough skin. Lots of things can go wrong with desquamation.

For example, dehydrated skin that lacks water doesn't come off properly. Your skin turnover also slows down as you get older. Alpha hydroxy acids help loosen skin cells so that they come off more easily.

It's not 100% established exactly how AHAs do this, but so far we think that they bind to calcium ions which makes the dead skin cells break up. The dead skin cells come off more easily and in smaller, less noticeable pieces. This means you end up with smooth clear glowing skin. AHAs also change other aspects of how skin works: it increases skin-plumping collagen and increases the proportion of younger cells in your skin. AHAs also reduce fine lines, prevent acne, fade dark spots, increase skin thickness, and even out skin tone and texture. They also act as humectant moisturizers that help your skin hold onto water.

There are a whole bunch of different AHAs that can help your skin out and they all have different properties. My favorite so far is glycolic acid, lactic acid, and mandelic acid. Glycolic acid is the smallest and most popular of the alpha hydroxy acids. It was my first AHA and I was so impressed when I tried it. I tried a sample of Paula's Choice 8% AHA Gel overnight and the next morning my skin was smooth, plump and glowing. Since glycolic acid is the smallest AHA it gets into the skin more easily and more deeply than other AHAs. This means that it will usually be more effective but it can also have more side effects.

Glycolic acid is the most irritating of the alpha hydroxy acids. It also has the most research to back it up. It's the active ingredient in a whole bunch of cult skincare products including P50 Lotion, Alpha H Liquid Gold, and Pixi Glow Tonic. It's also commonly used in peels for treating acne and pigmentation, sometimes along with microdermabrasion or micro needling. If you're starting on a glycolic acid product I would recommend a leave-on product that's got lower than 10% concentration and a pH under 4 or 5.

You should also use sunscreen when you're using glycolic acid since it makes your skin more prone to sun damage even when it's not on your skin. You can use it in the morning or at night.

Lactic acid is the best-researched alpha hydroxy acid after glycolic acid and it's my current favorite and I use all of these products. Lactic acid is notable for being gentler, more hydrating and more effective at treating sun damaged skin. It also increases the ceramides in your skin.

Ceramides are one of the three oily lipids in your skin that's important in keeping your skin waterproof so your skin will stay hydrated. Like with glycolic acid I would recommend starting with a leave-on product with less than 10% lactic acid and a pH of 4 or 5, if you haven't tried any alpha hydroxy acids before. Lactic acid is also in yogurt but it's usually at less than 1%, so yogurt masks won't be anywhere near as effective as a leave-on product.

Mandelic acid is another alpha hydroxy acid and I've only recently started using it in this For Beloved One product. It's only really been studied in peels but it works a lot like glycolic and lactic acids. Because it's quite a bit larger than glycolic and lactic acids, mandelic acid doesn't penetrate as deeply so it's even less irritating and has a more even effect in peels. In peels it's commonly recommended for ethnic skin that's more prone to rebound hyperpigmentation, which is when an irritating treatment makes your skin more pigmented. Salicylic acid is a really popular anti acne treatment. It comes from willow bark and is structurally related to aspirin so it's got anti-inflammatory properties. It's also commonly referred to as a beta hydroxy acid. Much like alpha hydroxy acids if can exfoliate your skin and keep your pores clear, reducing acne.

You can find salicylic acid in lots of products like serums, spot treatments, and cleansers. It's usually at a concentration of 0.5 to 2 percent, although in spot treatments it's usually higher. It's also used in high concentration in peels for treating acne, acne scars, pigmentation, sun damage and age spots. You can also find it in wart and corn removers.

There's some evidence that pH isn't all that important for salicylic acid products, so if you want less irritation you can try a higher pH treatment. Azelaic acid is one of the key ingredients in lots of prescription-only acne creams. It's usually at 15 to 20 percent. There aren't many side effects to azelaic acid unless your skin is very sensitive, in which case it can give you a little bit of stinging, redness and peeling. You can also use azelaic acid to fade pigmentation, like post-acne marks, the brown marks that are left on your skin after you've had a pimple, also known as post-inflammatory hyperpigmentation or PIH.

In combination with retinoids, azelaic acid can work almost as well as hydroquinone. Retinoic acid is better known as tretinoin. It's the active ingredient in creams like Retin-a and Renova.

It is THE gold standard of anti-acne and anti-aging treatments. It's a form of vitamin A and it's backed up by tons and tons of studies. Tretinoin works by reducing clogged pores so you end up with less acne. It also increases the amount of collagen in your skin, which means it prevents wrinkles. It's also handy for fading dark spots.

Tretinoin is super awesome but it's also really irritating so when you use it a lot of people end up with red flaky itchy skin. It also causes purging. You can find tretinoin's weaker cousin retinol in lots of skin care products like this one. It's less effective but it's also a lot less irritating. Ascorbic acid is the most common water-soluble form of vitamin C. It's also the best-researched version.

Vitamin C has a whole bunch of awesome benefits for your skin like treating pigmentation and increasing collagen. Ascorbic acid is an antioxidant that protects the skin from damaging free radicals that are made by UV radiation and environmental pollution. These are one of the main causes of skin aging. The biggest problem with ascorbic acid is that it breaks down in water really quickly. If it's combined with other antioxidants like vitamin E and ferulic acid it breaks down way more slowly, but this also tends to make the product really expensive. I usually make my own DIY vitamin C serum so I can make sure it's fresh and save money.

You can also find more stable forms of vitamin C in skin care like magnesium ascorbyl phosphate and tetraisopalmitoyl ascorbic acid, but there's a lot less research on these. Linoleic acid is a fatty acid that we usually find in skincare oils. The difference between linoleic acid and other acids is when we're talking about linoleic acid in oils, it's actually been reacted to lose the acid group and it forms a triglyceride, so it won't donate H+. Linoleic acid by itself can lighten pigmentation, but in oils, most of the linoleic acid won't be free to lighten your pigmentation like it normally would.

But it isn't entirely useless in skincare oils. I personally love oils that are rich in linoleic acid because they tend to feel a lot lighter, which is really nice when you have oily skin like me. That's a quick overview of my favorite skincare acids. Do you use acids? Did I forget to talk about your favourite one? Let me know in the comments! If you liked this video please subscribe to my channel, check out my blog, and follow me on Instagram. I also have a free exfoliation guide on my blog which you might be interested in if you want to find out more about acids. See you next time for more beauty science! :).

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