Nurtureholiks Clear Serum

In vitro studies have shown that Rosa damascena can scavenge free radicals and reduce melanin overproduction. Research has also found this extract offers some degree of UV absorption but this should not replace your sunscreen.

Unlike most brighteners that target tyrosinase (the enzyme that synthesizes melanin), TXA works further upstream. It basically blocks your cells from receiving the signal to produce pigment.

This makes it one of the rare actives that works on three pathways at once:

This makes it effective for treating melasma, post-inflammatory hyperpigmentation (PIH), and sun-induced dark spots.

The most effective cosmetic concentration sits between 2-5% and going higher doesn't boost results.

Side effects are generally mild; occasional irritation, flaking, or dryness have been reported at the start of use. Overall, this ingredient is pretty well tolerated, even by sensitive skin types.

Another perk of this ingredient is that it does not cause photosensitivity, so it's safe to use in the AM and PM.

By latching onto the copper that the enzyme tyrosinase needs to function, Kojic Acid prevents less pigment from being made. It's so well-established that researchers regularly use it as the go-to benchmark when testing new brightening ingredients.

Some other perks include documented antioxidant and antimicrobial properties. The The CIR (Cosmetic Ingredient Review) Expert Panel concluded Kojic Acid is safe for use in cosmetic products at concentrations up to 1% and the EU's SCCS (Scientific Committee on Consumer Safety) considers it safe as a skin lightening agent at concentrations up to 0.7%.

One thing to know about Kojic Acid is that stability is its weak spot; it is sensitive to light, heat, and air exposure and will oxidize/turn brown in formulations. Its derivative, Kojic Dipalmitate, was developed as a stable alternative.

Some individuals have reported contact sensitization so be sure to patch test if you have reactive or sensitive skin.

Fun fact: It was first discovered in 1907 and naturally occurs in the production of sake, soy sauce, and miso.

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.

One manufacturer claims this ingredient to have a pH range of 2-8 and to be biodegradable.

This ingredient is also known as Sepimax Zen.

It does have a penetration-enhancing reputation that is a bit more nuanced than marketing suggests; a cell study on human skin found that 10% DMI didn't significantly boost the permeation of Hydroquinone, Salicylic Acid, or Octadecenedioic Acid compared to controls (though it did improve their solubility in the formula itself).

Typical usage concentrations usually range from 1-10% depending on the formula's needs; this ingredient is also well tolerated at these levels.

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.

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.

The only catch is that HA isn't a single thing; it actually comes in a wide range of molecular weights (~50 - 2,000+ kDA) and size matters.

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

This is why the best HA serums blend the two sizes together so you get the best of both worlds.

The majority of cosmetic HA is produced by bacterial fermentation, typically using Streptococcus or Bacillus strains. Typical use levels in skincare sit around 0.1-2%.

A clinical study using a 0.2% low-molecular weight HA gel showed improvement in facial seborrheic dermatitis with excellent tolerance.

These are some other common types of Hyaluronic Acid:

This ingredient contains a group of yellow pigments called curcuminoids (mostly curcumin) that give it genuine antioxidant and anti-inflammatory activity in skin.

Reviews of topical clinical studies have found turmeric/curcumin to be generally well-tolerated and useful across conditions like eczema and mild inflammation.

One thing working in its favor is that curcumin barely penetrates; in lab skin-permeation testing, the curcuminoids mostly stayed in the outermost layer of skin. This is a good thing because its soothing and antioxidant activity is a surface-level job anyway.

At this time, industry data shows there's no single "correct" cosmetic percentage. It's used across a wide range depending on the product and varies from tiny fractions of a percent up to a few percent.

Allergy-wise, curcumin is a documented (but uncommon) contact allergen. It can also cross react with related plants, so anyone with a turmeric/ginger/cinnamon allergy or reactive skin should patch test first.

It's actually inactive on its own and works like a slow-release "storage" form; the enzymes in your skin called esterases gradually convert it into active vitamin E over time.

One in vivo study showed 5% of the acetate in the living layer of the epidermis converted to vitamin E after 5 days of application. This study also found the skin gained protection against UV damage even though the conversion was slow and small.

Once converted, vitamin E acts as a skin's main fat-soluble antioxidant that fights free radicals to protect skin from damage.

Topical vitamin E generally boosts the skin's photoprotection, and it reduced UV-damage in animal models.

This ingredient has some brightening potential but it's more of a prevention ingredient than spot-fader. Cell studies show it can slow down melanin production but it's worth noting that it's not the most powerful brightener out there.

Overall, it has a pretty solid safety profile and has been found to be non-irritating and non-comedogenic. Allergic reactions may happen but stay rare due to how widely the ingredient gets used.

The concentration will vary depending on the formula; industry data shows 0.1% in baby lotions, 3% in lipsticks, and 5% in foot powders. You can also find this ingredient at 100% in a pure vitamin E oil.

Most leave-on skincare keeps it at the lower end, often between 0.5-1%.

Lycopene is a potent antioxidant. Besides helping to protect your skin against free-radical molecules, it also helps soothe the skin. Lycopene gives watermelon the distinct red color.

The CIR Expert Panel has confirmed this ingredient to be nontoxic and clinical studies show no sensitization at cosmetic use concentrations.

True allergic reactions are quite rare: a 15-year retrospective study of 6,751 patients found only 0.31% had a positive reaction (and less than half were considered clinically relevant).

It seemed that when sensitization does occur, it's most commonly linked to topical medication (like corticosteroids) and not cosmetics. Allergic contact dermatitis also appears largely limited to individuals with underlying skin conditions.

Overall, propylene glycol is a well-studied ingredient that most people can tolerate without issue.

Some people who are allergic to imidazolidinyl urea also react to diazolidinyl urea. It ranked as the 14th most common allergen in patch tests from 2005–06.

Safety reviews show that at concentrations under 0.5%, the formaldehyde released remains below the accepted safety limit, making it considered safe for cosmetic use.

Ultimately, its safety depends on individual skin sensitivity and personal comfort with formaldehyde-releasing preservatives.

It is typically used at very low levels in cosmetics, with most formulations using 0.0125% or less (well below its approved maximum).

In the EU, IPBC concentration limits are set at 0.02% in rinse-off products and 0.01% in leave-on products.

Though IPBC is a relatively uncommon contact allergen, patch testing studies show positive reaction rates ranging from 0.3%-0.9% of patients tested. This is still quite low compared to preservatives like methylisothiazolinone which sits at around 4-5%.

Researchers note that existing iodine sensitives or rubber allergies may be the cause of this as IPBC shares a structure with both thiuram (used in rubber) and iodine.

Be sure to patch test if you are unsure and speak with a medical professional about using this ingredient.