XYZ SKIN Star Bright Serum

Another interesting compound that makes it stand out from other oils is the trace amount of all-trans retinoic acid (the same molecule as prescription tretinoin), along with some carotenoids and tocopherols.

The linoleic acid is a precursor to ceramide 1, one of the essential lipids in the stratum corneum. Topical linoleic acid application has been shown to improve barrier function and reduce comedone size in clinical studies.

One study found that linoleic acid and alpha-linoleic acid lighten UV-induced hyperpigmentation. A 2015 study found that participants who used rosehip twice daily for eight weeks saw improvements in crow's feet, skin moisture, and skin elasticity compared to the placebo.

If you're hoping to get tretinoin benefits from this ingredient, it's worth noting the trans-retinoid acid is trace-level and minimal compared to the amount of retinol or tretinoin found in formulas.

A 2024 review highlighted the fatty acid composition in rosehip-based dermatological products for:

Typical usage rates range from 1-100% with 5-10% being the most common in moisturizers.

Since the oil is high in polyunsaturated fatty acids, it's prone to oxidation. Look for formulations stabilized with ingredients like vitamin E and be sure to store away from light/heat.

Fungal acne: This oil is not considered fungal acne safe because dominant fatty acids fall into the C11-24 range that Malassezia can metabolize.

Because it’s oil-soluble, THD dives deep into your skin’s fatty layers (think ceramides and cholesterol) to fight off the kind of free radicals that mess with your skin barrier. This makes it a great pair with water-based vitamin C (ascorbic acid) that mainly works on the surface.

Even at just 0.1%, THD is already showing great antioxidant activity. When used up to 2%, it helps keep your skin happy and calm, especially when it’s stressed from pollution or sun.

Want to fade dark spots or tackle hyperpigmentation? You’ll want 5% or more. Pairing it with brightening buddies like niacinamide or licorice root gives even better results. One study even used 30% THD with other brighteners and saw real results on stubborn discoloration, even in melasma-prone skin.

A note on THD: It’s has a slightly silky, oily texture and usually shows up colorless or pale yellow (though the exact shade can vary by supplier).

While you can sneak it into water-based formulas, it really shines when paired with silicones or oils, which help your skin soak it up better.

THD is pretty stable, but it’s still vulnerable to degradation like ascorbic acid. Too much light or heat (above 113°F / 45°C) can break it down over time. Go for dark and opaque packaging that keeps it safe and shady!

Read more about other types of Vitamin C:

This oil is rich in fatty acids, including: two types of linoleic acid (~30-34%), oleic acid (17%), and palmiteic acid (35%). Note these numbers are averages, and different parts of the plant will vary.

Palmitoleic acid has been shown to help soothe inflammation and promote wound healing. It is also naturally found in the fat of our skin.

Overall, seabuckthorn oil is great for nourishing, hydrating, and soothing skin. While it shows UV protecting properties, it should not replace sunscreen.

Due to the rich fatty acid content, this ingredient may not be Malassezia folliculitis, or fungal acne, safe.

Seabuckthorn berries are little orange fruits. This plant is native to Asia.

They contain shikimate dehydrigenase, an enzyme shown to help reduce inflammation and soothe the skin.

The amino acids found in cucumbers help nourish our skin's natural acid mantle (it's an important part of our skin barrier). This slightly acidic film acts as a barrier to protect us from bacteria, viruses, and other contaminants.

Unless you have an allergy to cucumbers, this is generally a non-irritating ingredient.

Fun fact: Cucumis Sativus is native to South Asia and can now be found on every continent.

It is generally considered low risk when used at the small amounts typical in cosmetics. However, it may still bother fragrance-sensitive skin because it’s a fragrant botanical.

Unlike some citrus peel oils, bitter orange flower extracts are not usually linked to sun sensitivity.

Topically applied tocopherol has been shown to protect against UV damage by ramping up the skin's own natural defense enzymes.

It also acts as a skin conditioning agent; some studies show that regular topical use can improve the skin's water-binding capacity over 2-4 weeks.

This ingredient is especially loved for being a team player. When combined with Vitamin C, the photoprotective effect of both ingredients roughly doubles and the combo also helps reduce UV-induced DNA damage.

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.

In formulations, it also serves as a stabilizer that helps protect other oxidation-prone ingredients from degrading.

Concentrations usually range from 0.1-1% in most leave-on products.