the klog Hydra Shield Anti-Pollution Jelly Toner

Dipropylene glycol is technically an alcohol, but it belongs to the glycol family (often considered part of the ‘good’ alcohols). This means it is hydrating and gentle on skin unlike drying solvent alcohols like denatured alcohol.

As a masking agent, Dipropylene Glycol can be used to cover the smell of other ingredients. However, it does not have a scent.

Studies show Dipropylene Glycol is considered safe to use in skincare.

You might have heard of "niacin flush", or the reddening of skin that causes itchiness. Niacinamide has not been found to cause this.

In very rare cases, some individuals may not be able to tolerate niacinamide at all or experience an allergic reaction to it.

If you are experiencing flaking, irritation, and dryness with this ingredient, be sure to double check all your products as this ingredient can be found in all categories of skincare.

When incorporating niacinamide into your routine, look out for concentration amounts. Typically, 5% niacinamide provides benefits such as fading dark spots. However, if you have sensitive skin, it is better to begin with a smaller concentration.

When you apply niacinamide to your skin, your body converts it into nicotinamide adenine dinucleotide (NAD). NAD is an essential coenzyme that is already found in your cells as "fuel" and powers countless biological processes.

In your skin, NAD helps repair cell damage, produce new healthy cells, support collagen production, strengthen the skin barrier, and fight environmental stressors (like UV and pollution).

Our natural NAD levels start to decline with age, leading to slower skin repair, visible aging, and a weaker skin barrier. By providing your skin niacinamide, you're recharging your skin's NAD levels. This leads to stronger, healthier, and younger looking skin.

Another name for vitamin B3 is nicotinamide. This vitamin is water-soluble and our bodies don't store it. We obtain Vitamin B3 from either food or skincare. Meat, fish, wheat, yeast, and leafy greens contain vitamin B3.

The type of niacinamide used in skincare is synthetically created.

Your skin makes glycerin on its own (mostly from sebaceous oil breakdown) and shuttles it to your outermost layer of skin, or your epidermis, via aquaporin-3.

Aquaporin-3 is a transporter that is essential for normal skin hydration, elasticity, and repair. Interestingly, mice lacking in AQP3 have dry and less elastic skin that can be fully corrected with glycerin.

This ingredient is non-irritating, plays well with almost every ingredient, and works across all skin types. Typical use is anywhere between 3-10% but can go up to 79% in some leave-on products.

Just know very high concentrations (>40%) can feel tacky in low humidity.

Glycerin is the name for this ingredient in American English. British English uses Glycerol/Glycerine.

That's where Acetyl Tetrapeptide-40 comes in. It turns down the signals that cause this inflammatory overreaction. As a bonus, keeping inflammation in check also protects collagen and other structural proteins from being broken down by enzymes.

According to a manufacturer, this ingredient also calms UV-related inflammation and helps reduce excess pigment production.

This ingredient is considered safe for all skin types and has been shown to work at low concentrations (0.05%).

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.

Snow mushroom is rich in polysaccharides, giving it moisturizing benefits. As a humectant, snow mushroom helps draw moisture from the air to the skin. Polysaccharides are able to mimic our skin's natural carbohydrates to help the skin retain water.

Snow mushroom has been shown to help with anti-aging due to its antioxidants. It increases the presence of superoxide dismutase in our brain and liver. Superoxide is a by-product of oxygen metabolism. It left unregulated, superoxide causes cell damage. Thus, superoxide dismutase acts as an antioxidant to protect our living cells.

Another study from 2016 showed snow mushroom extract blocks the skin from creating melanin when exposed to UVB. Thus, it may help protect against the signs of aging from sun exposure. However, more studies are needed to confirm this. Another study from 2021 found snow mushroom to protect against UVA damage as well.

This white mushroom is native to Asian countries such as China, Korea, Japan, and Thailand. It is a common ingredient in traditional Chinese cuisine and medicine.

It's pretty compatible with most ingredients, but just sure to space out enzyme products with strong acids/retinoids to avoid over-doing it.

Maximum reported concentration is around 0.1% and most leave-on products use just 0.05%. If you see higher figures like 5-10%, this is usually the pre-diluted material from raw extract suppliers.

This ingredient has an assuring safety record and there's a lack of clinical case reports of dermatitis from using it.

The only caveat is allergy: patch test if you have a papaya or latex-fruit allergy.

Licorice Root also contains a flavonoid. Flavonoids are a natural substance from in plants. Flavonoids also have antioxidant properties.

Another component, glycyrrhizin, has been found to have anti-inflammatory and antimicrobial benefits. This may make licorice root extract effective at treating acne. However, more research is needed to support this.

Liquiritin is one of the flavone compounds found in licorice. It has been found to help lighten skin by preventing tyrosinase from reacting with tyrosine. When the two react, protein is converted to melanin. Melanin is the substance in your body that gives your features pigmentation.

Studies show the compounds in centella help with:

The combination of all these properties makes centella effective at soothing, hydrating, and protecting the skin.

Other great components of centella include Vitamin A, vitamin C, several B vitamins, and Asiatic Acid.

Fun fact: Centella has been used as a medicine and in food for many centuries. As a medicine, it is used to treat burns, scratches, and wounds.

Bamboos are rich in Vitamin E, Vitamin B6, and copper.

A recent study found bamboo extract might interrupt the process of hyperpigmentation.

Research shows it can encourage your skin cells to turn over and renew by stimulating keratinocyte and fibroblast proliferation.

It also has mild keratolytic properties to help loosen and shed dead skin cells without being harsh.

Studies also suggest allantoin can help calm inflammation by dialing down some of the chemical signals your skin sends out when it is irritated.

This ingredient is typically used in the 0.1-0.5% range, and the FDA recognizes it as a skin protectant in OTC products up to 2%.

Overall, allantoin is a wonderful addition to most routines; it is stable across a wide pH range (~4-8), works well with other ingredients, and is considered non-sensitizing/non-irritating.

Fun fact: Allantoin is naturally occurring in comfrey root, beets, chamomile, and wheat sprouts. Our bodies even produce it as a byproduct of uric acid metabolism.

Though this ingredient works well with most skin types, some people with sensitive skin may experience a reaction such as allergic rashes, closed comedones, or itchiness.

Tromethamine helps balance the pH level of a product. Normal pH level of skin is slightly acidic (~4.75-5.5). The acidity of our skin is maintained by our glands and skin biome. 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.

Oral Tromethanmine is an anti-inflammatory drug but plays the role of masking, adding fragrance, and/or balancing pH in skincare.

1,3-Propanediol, 2-amino-2-(hydroxymethyl)-

It can also form a thin protective film on skin. One study found that a formula using this polymer helped slow down how quickly other ingredients (like DEET) were absorbed through skin.

A 2024 study of over 1,300 patients confirmed that sensitization to this ingredient is rare. It is also non-mutagenic and has a clean track record.

Industry-reported use ranges from 8% in rinse-off products and 2% in leave-on formulations.

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.

Because it is not a free-fatty acid, this ingredient is fungal acne safe (there's nothing for Malassezia to feed on).

The high vitamin C content of Kakadu plum also helps lighten skin. Vitamin C has been shown to block the process of skin darkening that leads to hyperpigmentation.

Kakadu plums have been used by indigenous cultures as medicine to help treat colds and as an antiseptic.

A high amount of carbomer can cause pilling or balling up of products. Don't worry, most products contain 1% or less of carbomer.

On top of that, this ingredient can counteract the effects of hard water by binding to the minerals in it.

One thing worth knowing is that Disodium EDTA has been shown to be a mild penetration enhancer. It can help other ingredients absorb into skin more effectively which can be a double-edged sword (great for actives, but can also make the active too strong if you have sensitive skin).

Clinical patch testing showed no significant skin irritation at typical use concentrations and minimal dermal absorption.

You'll most likely see this ingredient near the end of an ingredient list. It's typically found in concentrations less than 1%.

Is it bad for your skin?

The answer comes down to concentration. Patch and wash studies have found highly concentrated alcohol-based hand rubs (60-100%) cause less barrier disruption than washing with a basic detergent like SLS. The only measurable effect in these studies was a temporary dip in skin hydration.

Concentrations below 12-15% in leave-on cosmetics is generally well-tolerated. Concentrations above start to see increased transepidermal water loss (TEWL) and reduced hydration.

In concentrations about 58%, it creates temporary channels in your skin's lipid layers to become more permeable and allow other ingredients to slip through easily.

This ingredient can be up to 80% of the formula in alcohol-based perfumes.

Overall, this ingredient is probably harmless if found lower down an ingredients list but worth side-eyeing if it's high up (especially if your barrier is already struggling).

Alcohol can worsen dry skin, eczema, and oily skin, especially at higher concentrations. This is because it can increase transepidermal water loss and decrease hydration to disrupt the skin barrier.

According to the National Rosacea Society based in the US, you should be mindful of products with these alcohols in the top half of ingredients.

True allergic contact dermatitis to ethanol is uncommon, but be sure to patch test if you have dry or sensitive skin.