Lactic acid vs Salicylic acid 

If you’ve searched for a solution to lessen your acne in the past it’s likely you came across numerous ‘acids’ – with lactic acid and salicylic acid being just a few within the (seemingly endless) pool of skincare. Both of these acids work by exfoliating your skin, albeit in different ways. This exfoliation helps to decrease the risk of clogged pores, which usually exacerbate acne. Despite this common feature, there are a lot of differences between these two lactic acid and salicylic acid, and understanding these differences allows you to get the most out of your skincare routine. 

What is Lactic acid?

As its name suggests, lactic acid is a derivative of lactose – the sugar commonly found in milk. However, there are also many other food and drink items which contain lactic acid, and are vegan! This is because lactic acid is created by certain bacteria during fermentation, which occurs to create wine, bread and pickled foods. It’s worth noting lactic acid can also be created artificially, so it’s always worth checking the source on your skincare packaging. 

Benefits of Lactic acid

• Increases cell turnover, meaning dead skin cells are shed from the surface of the skin more often (as lactic acid dissolves the bonds holding them together on the surface) and the production of new skin cells is sped up. This process really helps to reduce how dull skin looks, as well as speeding up fading of scarring and pigmentation
• Reducing acne and fine lines, as the process outlined above reduces the amount of dead skin cells available to clog pores which is a major contributor in the formation of acne. Fine lines often appear due to dehydrated, dry or rough skin. The increased removal of skin cells allows for dry and rough skin to be a thing of the past! Interestingly lactic acid also stimulates collagen, plumping the skin and making it firmer – hence reducing the appearance of wrinkles.
• Moisturizing skin, as lactic acid acts as a humectant (a molecule which attracts and retains moisture) and also is a key part of the skin’s NMF – natural moisturizing factor. The NMF is a group of water soluble compounds which allow the skin to naturally hydrate itself, and when it isn’t replenished skin tends to dry out. To keep the NMF functioning well it’s important for the skin to be rich in those water soluble compounds, one of which is lactic acid. By topically applying lactic acid it allows for higher levels of NMF, and more hydrated skin. Interestingly lactic acid also stimulates ceramide production, which are a key building block in skin barrier health. 

Risks of Lactic acid 

• Increased sensitivity to the sun, which occurs with most exfoliants. This sensitivity means your skin is more likely to burn when exposed to the sun, as well as an increased risk of skin cancers. This risk can be mitigated by ensuring proper use of SPF, and avoiding the times during the day of most intense sunlight (10-2).

What can Lactic acid be used for?

Lactic acid has many uses, not just as an exfoliator! As we’ve previously touched upon, it helps to moisturize the skin. This coupled with its exfoliation properties allow fine lines and enlarged pores to be improved. 

When, and How often should you use Lactic acid?

This is a tricky question to answer, as it will vary depending on the product you have and how sensitive your skin is, as well as your previous use of exfoliating acids. Lactic acid is commonly found in serums, moisturizers and face masks, with face masks often being the most potent due to their intended use being for a short time, followed by removal of the mask. A general guideline of how to use each type of product is below (remember lactic acid should only be used at night)

Serums : Initially I would use this twice a week,  ensuring hydrating and nourishing serums are used either side of the acid exfoliator. If you find this suits your skin nicely, the frequency could be increased to 3 times a week, but if your skin begins to feel tight or is red, drop this down to once a week. 

Moisturizers : These are likely to be the least potent, as the lactic acid will be mixed in with a creamy formula alongside skin-supporting ingredients like ceramides, niacinamide or polyglutamic acid. 

Masks : Typically acid masks instruct being left on for 10-15 minutes, but this is a time I wouldn’t attempt before several weeks of building up to this. Initially I would do 3-5 minutes, to see how my skin would react. If skin reacts positively, the following week this could be increased to 6-8 minutes, and increase the time using the mask each week until you find the optimum for your own skin.

What skin types should use Lactic acid?

Lactic acid is ideal for all skin types, as it isn’t as potent as other AHA’s. This means sensitive skin can usually tolerate it, and it works for dry skin types because of the moisturizing effect. 

What is Salicylic Acid?

Salicylic acid is a type of beta hydroxy acid – a similar molecule to lactic acid, but having enough differences to make it act in a completely different way when applied to the skin. Whilst lactic acid is water soluble, salicylic acid is oil soluble meaning it can dive deep into pores. Salicylic acid can either be artificially made, which is the likely origin when you see ‘salicylic acid’ on an ingredient list, or it can be naturally found in the leaves of the wintergreen plant, or willow bark. 

Benefits of Salicylic Acid

• Reducing inflammation and redness, which isn’t surprising as salicylic acid belongs to the chemical family of salicylates which are the active compound within aspirin. Aspirin is known for its anti-inflammatory effects, so it’s unsurprising that salicylic acid also has this effect. Whenever inflammation is reduced, redness also usually subsides.
• Reducing acne, as a root cause of pimples is pores clogged with sebum, and other debris. As salicylic acid is oil soluble it can work from inside the pore, which allows it to break down the sebum, meaning that the pores don’t clog as easily. A closed clogged pore is known as a whitehead, whereas a blackhead is an open clogged pore. 
• Regulates oil, meaning that less oil is produced by any overactive oil glands (which is common for people with acne) and skin won’t have that horrible greasy feeling at the end of the day.
• Enlarged pores may be reduced, due to enlarged pores normally occurring due to their congestion. By easing this congestion, it allows pores to return to their original (and smaller!) size. 

Risks of Salicylic Acid

• Increased sensitivity to the sun. Just like lactic acid, salicylic acid speeds up cell turnover, and hence leaves skin more vulnerable to the impact of the sun. This makes it more important to wear SPF during the day, and use stronger BHA products at night. 
• Irritation is more likely to occur, especially if you overuse your products! As salicylic acid is oil soluble, and helps to decrease the production of oils using it too much may dry the skin out too much. This often makes the skin look irritated, appearing as red and flaky skin. 

What can salicylic acid be used for?

Salicylic acid is fantastic at decongesting pores, as well as lessening the formation of blackheads and whiteheads. Salicylic acid is also often used within body care products, as body acne is something very common!

When and How often should you use it?

Salicylic acid tends to be less sensitizing to the sun, meaning most people find it okay to use in the morning (as long as adequate SPF is applied.) Personally I prefer to use salicylic acid in the mornings, as I then have no overlap upon my evening routine with retinol or other acids (like azelaic, lactic or mandelic.) It’s always best to avoid mixing acids together, as they are usually strong ingredients and mixing them together greatly increases the risk for irritation. 

As with lactic acid I would always build up my use with salicylic acid, for example using the toner perhaps 4 times a week, building this up. If it is a weaker product it may be suitable for daily use, whereas a stronger serum I would recommend alternating with a hydrating serum, every other day. 

What skin types should use it?

Salicylic acid is ideal for supporting oily, combination and acne-prone skin types. 

So, what’s the difference between AHA and BHA’s?

Both AHA’s and BHA’s are exfoliating acids, so you might imagine they are quite similar. They act in different ways, and hence target different concerns. AHA’s act much more at the skin surface due to their water-soluble nature, dissolving the ‘glue’ between dead skin cells causing them to be removed from the skin. This means AHA’s are fantastic for dull and congested skin. BHA’s on the other hand are oil-soluble, meaning they can dive deep into the pores. Here BHA’s work to break down sebum and debris, clearing pores and helping to reduce oil production. 

Can Lactic acid and Salicylic acid be used together?

Whilst on paper this pairing isn’t problematic – meaning they don’t become chemically unstable or reactive when applied to the skin together, as both can sensitize or irritate skin applying them together increases this risk. Personally, I would not mix the two – use salicylic in your morning routine, and then lactic acid in your evening routine a few times a week. 

Lactic acid or Salicylic acid for acne?

When treating acid salicylic acid is supreme, it specifically targets oil within the pores which benefits acne-prone skin in many ways. This includes less sebum for acne bacteria to ‘feed’ off, as well as generally clogging pores. It’s worth noting a small percentage of people have salicylate sensitivity, so if you find many more pimples appearing it may be worth laying off the salicylic acid. 

Lactic acid or Salicylic acid for exfoliation?

Lactic acid hands down in my opinion, as it works at the surface of the skin so the impact of its exfoliation is much more obvious – less dull skin, with a more even tone is revealed. 

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