Peter Thomas Roth PRO Strength 10% PHA Exfoliating Clarifying Liquid

As a surfactant, isopentyldiol is a hydrotrope. Hydrotropes help surfactants (cleansing agents) dissolve into water.

According to the manufacturer, using this ingredient with sorbitol boosts skin hydration and helps close cuticles of damaged hair.

This ingredient is water-soluble.

Your skin has a natural pH and acid mantle. This acid mantle helps prevent harmful bacteria from breaking through. The acid mantle also helps keep your skin hydrated.

"Alkaline" refers to a high pH level. A low pH level would be considered acidic.

Specifically, AHAs work by breaking down the structural "glue" holding the old skin cells in place. Getting rid of the old skin cells allows skin to regenerate newer skin cells in its place. A build up of dead skin cells can lead to tired and dull looking skin.

Due to this, glycolic acid helps with:

Fun fact: Glycolic acid increases skin hydration by playing a role in creating molecules that create hyaluronic acid naturally.

When starting glycolic Acid, it is normal to feel slight stinging.

The pH value and concentration of glycolic acid play a role in the effectiveness of the product. Concentrations between 5-20% glycolic acid have been shown to be effective in clinical studies.

Recent studies have shown Glycolic Acid may protect the skin against UV damage. However, you should always wear SPF, especially when using exfoliants.

Read more about some other popular AHA's here:

Unless it is specified to be non-alcohol, many types of witch hazel ingredients are distilled in denatured alcohol.

Witch Hazel water is an astringent, anti-inflammatory antioxidant, and antibacterial ingredient.

It contains tannins. Tannins have a drying effect when used on skin by constricting proteins. The constriction also minimizes the appearance of pores.

Both the tannins and fragrance found in witch hazel may be skin-sensitizing.

Witch hazel water gets anti-inflammatory and antibacterial properties from its catechin and gallic acid content.

Indigenous groups have used witch hazel to help treat inflammation in North America for centuries.

Not only does it help exfoliate the skin, it helps strengthen the skin's barrier. When applied, lactic acid helps the skin create ceramides.

Lactic acid is an over-the-counter chemical exfoliant that comes from the fermentation of lactose — a carbohydrate found in milk.

Legend has it that Cleopatra used to bathe in sour milk to help reduce wrinkles.

Read more about some other popular AHA's here:

Ethoxydiglycol also helps deliver other key ingredients into the skin.

Unlike AHAs which are water soluble, Salicylic Acid is oil soluble. This means that it's able to exfoliate the inside of pores and reduce blackheads.

Concentrations of 0.5-2% are recognized by the U.S. FDA as an over-the-counter topical acne product.

It can cause irritation and/or dryness if one's skin already has a compromised moisture barrier, so it's best to focus on repairing that before introducing a Salicylic Acid into your routine.

In general, Salicylic Acid is a great ingredient for oily acne-prone skin.

While salicylic acid does not increase sun-sensitivity, we still recommend wearing SPF.

If you are looking for the ingredient called BHA or Butylated Hydroxyanisole, click here.

Like salicylic acid, this ingredient is a chemical exfoliant that can help break down the oil in your pores and reduce inflammation.

Though studies for LHA do show it to be less effective than salicylic acid. To be fair, salicylic acid is the reigning monarch of acne treatments.

However, a study from 2009 found LHA to be comparable to BPO, making it a good alternative for people with sensitive skin. Another study of 14 patients found a significant decrease in comedones after using LHA.

Another pro of LHA? It is less irritating than salicylic acid due to its large molecule size.

Large molecules cannot penetrate skin as well, so they are gentler on the skin. LHA is much less penetrative than salicylic acid.

An in-vitro study (not done on a living organism) found only 6% of LHA penetrated past the statum corneum compared to 58% of salicylic acid. An in-vivo (done on a living organism) analysis revealed ~17% of LHA was still present in the top layer of skin after 4 days, versus ~9% of salicylic acid.

Interestingly, a study from 2008 found LHA comparable to another famous acid, glycolic acid.

This study found about 10% of LHA is as effective as 20-50% of glycolic acid in treating hyperpigmentation and fine-lines.

Hydroxy acids have been found to stimulate skin protein, lipids, and thermal thickening. This may have anti-aging benefits.

Due to their hygroscopic nature, they act as both humectants and emollients. Humectants draw moisture from the air to your skin, while emollients help trap moisture in.

The phospholipids in our skin can be naturally depleted. Replenishing the phospholipids in our skin can help hydrate your skin.

Studies show phospholipids display antioxidant activity and may help with reducing the signs of aging.

This ingredient is non-occlusive.

Some types of phospholipids:

Ascorbyl Palmitate is oil soluble.

Read more about other types of Vitamin C:

Another benefit is a bit of UV protection. Vitamin E helps reduce the damage caused by UVB rays. (It should not replace your sunscreen). Combining it with Vitamin C can decrease sunburned cells and hyperpigmentation after UV exposure.

You might have noticed Vitamin E + C often paired together. This is because it is great at stabilizing Vitamin C. Using the two together helps increase the effectiveness of both ingredients.

There are often claims that Vitamin E can reduce/prevent scarring, but these claims haven't been confirmed by scientific research.

As an emollient, lecithen helps soften the skin and creates a barrier to keep moisture in.

As an emulsifier, it also helps prevent water and oil ingredients from separating. Lecithin can also help ingredients be better absorbed by the skin.

This is because the phospholipids in lecithin produce liposomes. Liposomes help other ingredients get through the skin barrier.

Depending on the source of this ingredient, lecithin may not be fungal acne safe. This is because some sources of lecithin come from soybean oil, which may feed the malassezia yeast that feeds fungal acne.

We recommend reaching out to the brand you are purchasing from to inquire about the source of their lecithin.

Both potassium sorbate and sorbic acid can be found in baked goods, cheeses, dried meats, dried fruit, ice cream, pickles, wine, yogurt, and more.

You'll often find this ingredient used with other preservatives.

Sodium benzoate works as a preservative by inhibiting the growth of bacteria inside of cells. It prevents the cell from fermenting a type of sugar using an enzyme called phosphofructokinase.

It is the salt of benzoic acid. Foods containing sodium benzoate include soda, salad dressings, condiments, fruit juices, wines, and snack foods.

Studies for using ascorbic acid and sodium benzoate in cosmetics are lacking, especially in skincare routines with multiple steps.

We always recommend speaking with a professional, such as a dermatologist, if you have any concerns.

In its pure form, Benzoic Acid looks like a white crystalline solid. It has slight solubility in water.

The name of Benzoic Acid comes from gum benzoin, which used to be the sole source of deriving this ingredient. Benzoic Acid is the most simple aromatic carboxylic acid.

Benzoic Acid is naturally occuring in strawberries, mustard, cinnamon, and cloves. It has a slight scent but is not considered to be a fragrance.

The acidity of our skin is maintained by our glands and skin biome; normal pH level of skin is slightly acidic (~4.75-5.5).

Being slightly acidic allows our skin to create an "acid mantle". This acid mantle is a thin barrier that protects our skin from bacteria and contaminants.

Disodium EDTA is a salt of edetic acid and is found to be safe in cosmetic ingredients.