Eucerin Hyaluron-Filler + Urea Day

It plays several roles in a formula:

Typical use levels for this ingredient sit around 1-10% and the Cosmetic Ingredient Review Expert Panel has affirmed safety at concentrations up to 25% in leave-on products.

Multiple assessments have found it to be non-irritating and non-sensitizing to most people.

However, there have been some cases of allergic contact dermatitis in patients with chronically compromised skin barriers.

Cetearyl alcohol has a comedogenic rating of 2 and irritancy rating of 1. Both of these numbers come from the 1989 study that used rabbit ears; a "2" means mildly comedogenic and a "1" means low irritancy.

Here's the catch: rabbit skin is more sensitive than human skin and throws a lot of false positives. A 1996 reappraisal found that ingredients rated 1-2 in the rabbit ear tests are generally safe for humans.

Remember comedogenic ratings are unable to assess the entire formula of a product or how it will react on your skin. Just be sure to patch test if you are unsure about certain ingredients.

This ingredient is not fungal acne safe. Cetearyl alcohol is a fatty alcohol with chain lengths that fall within the range that Malassezia can metabolize.

Urea has the strongest exfoliation effect in concentrations higher than 10%. It is a keratolytic agent, meaning it breaks down the keratin protein in the top layer of skin. This helps remove dead skin cells and flaking skin.

In medicine, urea has been shown to help increase the potency of other ingredients, such as fungal treatments.

Humans and animals use urea to metabolize nitrogen-containing compounds. Urea is highly soluble in water. Once dissolved, it is neither acidic nor alkaline.

Urea is actually one of the more well-studied and well-supported ingredients out there if you have eczema.

Clinical trials have shown that urea creams in the 5 - 10% range can:

Higher concentrations (20 -30%) can also help with thickened, scaly patches but is also more likely to sting on active flares.

Skip urea if you have rosacea. The AAD (American Academy of Dermatology) lists it alongside alcohol, menthol, and fragrance as a potential irritant for rosacea-prone skin. Urea's keratolytic and penetration-enhancing properties can trigger stinging, burning, and redness.

As always, your skin is unique, so definitely check in with your dermatologist.

Studies have found that avobenzone becomes ineffective when exposed to UV light (it is not photostable; meaning that it breaks down in sunlight). Because of this, formulations that include avobenzone will usually contain stabilizers such as octocrylene.

However, some modern formulations (looking at you, EU!) are able to stabilize avobenzone by coating the molecules.

Avobenzone does not protect against the UV-B range, so it's important to check that the sunscreen you're using contains other UV filters that do!

The highest concentration of avobenzone permitted is 3% in the US, and 5% in the EU.

Those who are using ketoprofen, a topical anti-inflammatory drug, may experience an allergic reaction when using octocrylene. It is best to speak with a healthcare professional about using sunscreens with octocrylene.

The EU allows a maximum of these concentrations:

High percentages of Sodium Lactate can have an exfoliating effect.

Fun fact: Sodium Lactate is produced from fermented sugar.

In vitro research found an increase in skin hydration by 58% and a decrease in TEWL by 37.8% after 24 hours of applying this ingredient (pretty impressive for a single ingredient!).

Besides hydration, shea butter also contains triterpenes that have anti-inflammatory potential. In particule, lupeol cinnamate has shown the highest anti-inflammatory activity in vivo.

Shea butter also contains vitamins A and E which may contribute to antioxidant activity.

While Shea Butter has an SPF rating of about 3-4, it is not a sunscreen replacement.

This ingredient may not be fungal acne safe because its fatty acids fall within the C11-C24 range that the Malassezia yeast can metabolize.

Dimethicone comes in different viscosities:

Depending on the viscosity, dimethicone has different properties.

Ingredients lists don't always show which type is used, so we recommend reaching out to the brand if you have questions about the viscosity.

This ingredient is unlikely to cause irritation because it does not get absorbed into skin. However, people with silicone allergies should be careful about using this ingredient.

Note: Dimethicone may contribute to pilling. This is because it is not oil or water soluble, so pilling may occur when layered with products. When mixed with heavy oils in a formula, the outcome is also quite greasy.

The content of sweet almond oil makes it a great emollient; it can help soften and hydrate your skin. Emollients create a barrier over your skin to trap moisture in. Sweet almond oil has antioxidant properties.

Those with an almond allergy should be careful of this ingredient and speak with a professional about using it in your skincare.

This ingredient may not be fungal-acne safe.

On top of that - it is highly photostable and helps prevent the photodegration of other sunscreen ingredients such as avobenzone.

Tinosorb S is allowed in the EU, Australia, and Asia. It is close to being approved by the FDA and we'll hopefully get this ingredient in the U.S. by late 2026.

Fun fact: Tinosorb S is the most effective UV absorber at maximum concentration (measured by SPF) permitted in the EU.

This ingredient is oil-soluble, so your oil-cleansers will take this right off at night.

Emollients help your skin stay smooth and soft. It does so by creating a film on top of the skin that helps trap moisture in.

Polymethylsilsesquioxane has not been shown to clog pores. It has been deemed safe to use up to 55%, but most cosmetics use much less.

If you have concerns about using this ingredient, we recommend speaking with a professional.

Interestingly, the size of the molecule affects its behavior:

Some clinical evidence links low molecular weight versions to improved wrinkle depth, elasticity, anti-inflammatory effects, and barrier repair.

Many serums use a blend of both weights so you can get surface hydration plus longer-lasting and deeper effects.

You'll typically see concentrations between 0.1-2% for this ingredient.

Antioxidants present in chondrus crispus include lutein and zeaxanthin. Lutein has the ability to filter blue light from screens.

One of the manufacturer for this ingredient states it is vegetable-based. It is also claimed to be stable at both high and low temperatures.

This ingredient may not be safe for fungal acne. We recommend speaking with a professional if you have any concerns.

As a preservative, it is used to stabilize products and prevent them from degrading. Specifically, BHT prevents degradation from oxidation.

The concerns related to BHT come from oral studies; this ingredient is currently allowed for use by both the FDA and EU.

However, it was recently restricted for use in the UK as of April 2024.

Its main job is chelation; this is a fancy word to say it grabs onto metal ions and neutralizes them. This is because even purified water in cosmetics contains trace amounts of metals that can cause big problems in a formula.

These trace metals can break down actives faster, cause discoloration, promote rancidity in oils, and make preservatives less effective. Trisodium EDTA binds to these metals and takes them out of the equation so your products can stay stable and effective for longer.

There's also an added bonus: by neutralizing the metals ions that bacteria need to thrive, this ingredient also acts as a preservative booster.

The Cosmetic Ingredient Review has concluded this ingredient to be safe as used in cosmetic formulations. It is not considered an irritant, sensitizer, and is barely absorbed through the skin.

Because lactic acid molecules are larger than glycolic acid, they don’t penetrate as deeply. This means they’re less likely to sting or irritate, making it a great choice for beginners or those with sensitive skin.

Like glycolic acid, it can:

Lactic acid also acts as a humectant (like hyaluronic acid). It can draw water into the skin to improve hydration and also plays a role in the skin's natural moisturizing factor (NMF) in the form of sodium lactate.

Studies show it can boost ceramide production to strengthen the skin barrier and even help balance the skin’s microbiome.

To get results, choose products with a pH between 3-4.

Lower strengths (5-12%) focus on surface exfoliation; higher strengths (12% and up) can reach deeper in the dermis (deeper, supportive layer) to improve skin texture and firmness over time.

Though it was originally derived from milk, most modern lactic acid used in skincare is vegan. It is made through non-dairy fermentation to create a bio-identical and stable form suitable for all formulations.

When lactic acid shows up near the end of an ingredient list, it usually means the brand added just a tiny amount to adjust the product’s pH.

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

Lactic acid is truly a gentle multitasker: it exfoliates, hydrates, strengthens, and brightens. It's a great ingredient for giving your skin a smooth, glowing, and healthy look without the harshness of stronger acids.

Read more about some other popular AHA's here:

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