Dermalogica Circular Hydrating Serum Versus Zakka Naturals Probiotic Skin Strength & Defense Booster Serum

1,2-Hexanediol is a synthetic liquid and another multi-functional powerhouse. 

It is a:

• Humectant, drawing moisture into the skin
• Emollient, helping to soften skin
• Solvent, dispersing and stabilizing formulas
• Preservative booster, enhancing the antimicrobial activity of other preservatives 

Butylene Glycol (or BG) is used within cosmetic products for a few different reasons:

• It is a solvent, meaning that it helps to dissolve other ingredients. This also enhances the absorption of the product into one's skin.
• It is a humectant, which means that it helps attract moisture into the skin.
• It helps improve product application.
• It has mild preservative properties.

Overall, Butylene Glycol is a safe and well-rounded ingredient that works well with other ingredients.

Hydroxyacetophenone is antioxidant with skin conditioning and soothing properties. It also boosts the efficiency of preservatives.

This ingredient is not irritating or sensitizing.

Lactic Acid is an AHA that is derived from fermenting lactose, a carbohydrate from milk. It removes the top layer of old and dead skin cells and helps increase cell turnover.

Benefits of Lactic Acid are that it can help to reduce large pores and reduce the effects of aging. Some potential downsides are that it can be bad for dry skin, cause irritation, worsen eczema, and worsen rosacea.

Sodium Hyaluronate is hyaluronic acid's salt form. It is commonly derived from the sodium salt of hyaluronic acid.

Like hyaluronic acid, it is great at holding water and acts as a humectant. This makes it a great skin hydrating ingredient.

Pentylene glycol is typically used within a product to thicken it. It also adds a smooth, soft, and moisturizing feel to the product. It is naturally found in plants such as sugar beets.

The hydrophilic trait of Pentylene Glycol makes it a humectant. As a humectant, Pentylene Glycol helps draw moisture from the air to your skin. This can help keep your skin hydrated.

Sodium PCA is the sodium salt of pyroglutamic acid. It is naturally occurring in our skin's natural moisturizing factors where it works to maintain hydration.

The PCA stands for pyrrolidone carboxylic acid, a natural amino acid derivative.

Xylitol is a humectant and prebiotic. It can help with dry skin.

In studies, xylitol has been shown to improve dry skin. It decreased transepidermal water loss, or when water passes through the skin and evaporates. Xylitol also showed to help improve the biomechanical properties of the skin barrier.

Lactobacillus Ferment is created by fermenting the Lactobacillus bacteria. It helps keep our skin's natural barrier and microbiome healthy.

Studies show lactobacillus ferment to be effective at repairing the skin barrier. Having a healthy skin barrier helps keep your skin healthy and hydrated. It also protects against bad bacteria.

Lysine HCl is an alpha amino acid salt.

Our skin uses amino acids as a precursor for building protein, and therefore keratins, collagen and elastin.

Betaine is a common humectant (a substance that promotes retention of moisture). It's known to be gentle on the skin and can help balance hydration.

This ingredient is best for improving hydration and soothing irritated skin. Studies also show it helps even out skin tone.

Sodium Lactate is the sodium salt of lactic acid, an AHA. It is a humectant and sometimes used to adjust the pH of a product.

This ingredient is part of our skin's NMF, or natural moisturizing factor. Our NMF is essential for the hydration of our top skin layers and plasticity of skin. NMF also influences our skin's natural acid mantle and pH, which protects our skin from harmful bacteria.

PCA is derived from amino acids and is naturally found in our skin's barrier.

As a humectant, PCA helps draw and hold moisture to the skin. Studies show it is effective at helping the skin stay hydrated long-term.

Serine is an amino acid naturally found in our body. Our bodies use amino acids to create protein.

Amino-acids help give keep our skin hydrated. They play an important role in the skin barrier, which keeps the skin plump and firm.

Alanine is an amino acid and is already found in the human body. Our skin uses alanine to build collagen, elastin, and keratin.

This ingredient is an amino acid that helps build proteins and moisturizes skin. It is already present in our skin as our bodies produce them naturally.

Glycine already plays a role in helping keep our skin moisturized as amino acids transport moisture throughout our skin.

Glutamic Acid is an amino acid that is found in all living organisms. Our bodies use this to help nerve cells in the brain communicate with other cells.

In cosmetics, glutamic acid is a famous humectant. It draws water from the air to your skin, keeping your skin hydrated (like hyaluronic acid).

Threonine is an amino-acid. It helps hydrate the skin and has antioxidant benefits.

Our skin uses threonine for creating collagen and elastin. Humans are not able to create threonine and must get it through eating foods such as fish, lentils, poultry, sesame seeds, and more.

Arginine is an amino acid that is important for human development. Your body uses is it to produce hair keratin and skin collagen.

As a cosmetic ingredient, Arginine has antioxidant properties and can also help repair damaged skin. This ingredient is derived either synthetically or from animals.

Proline is an amino-acid. It helps moisturize the skin and plays an important role in creating proteins.

Our skin uses proline as one of the building blocks for producing collagen.

Xanthan gum is used as a stabilizer and thickener within cosmetic products. It helps give products a sticky, thick feeling - preventing them from being too runny.

On the technical side of things, xanthan gum is a polysaccharide - a combination consisting of multiple sugar molecules bonded together.

Tetrasodium Glutamate Diacetate is a chelating agent. Chelating agents help prevent metal ions from binding to other ingredients. This helps prevent unwanted effects and reactions from a product. These metal ions may come from water and are found in miniscule amounts.

Tetrasodium Glutamate Diacetate can also help other preservatives be more effective.

Sodium Hydroxide is also known as lye or caustic soda. It is used to adjust the pH of products; many ingredients require a specific pH to be effective.

In small amounts, sodium hydroxide is considered safe to use. However, large amounts may cause chemical burns due to its high alkaline.