Dr. Sheth's Rosehip & Retinol Serum

Due to regulation loopholes, you'll likely see this ingredient in "100% mineral" sunscreens.

That conversion happens in two steps: your skin first turns Retinol into Retinaldehyde (also called Retinal), then turns Retinaldehyde into Retinoic Acid.

Retinol is converted to biologically active retinoic acid via retinaldehyde by dehydrogenases in a two-step oxidation process.

Each step is a little "upgrade" toward the active form which is part of why Retinol is gentler than prescription Retinoic Acid; your skin does the work gradually. This also explains where Retinol sits in the retinoid family.

Here is the retinoid family ranked roughly by strength: Retinyl Esters (like Retinyl Palmitate) < Retinol < Retinaldehyde < Retinoic Acid.

Retinoid activity increases in that order, while tolerance runs in reverse; retinyl esters are the gentlest and retinoic acid the most irritating.

The more conversion steps an ingredient needs, the gentler (and slower) it tends to be, so Retinol lands in a nice middle spot. It's more effective than the esters, gentler than prescription options.

Once it becomes Retinoic Acid, it binds to receptors inside your cells' nuclei (called RARs and RXRs). These receptor pairs bind to specific DNA motifs called retinoic acid response elements and act like switches that turn certain genes on or off.

In practice, this means a few things happen in a formula. It:

That last two are worth a closer look.

A study that tested Retinol directly (not just prescription Retinoic Acid) found that four weeks of retinol thickened the epidermis and switched on the genes for Collagen I and Collagen III, with more procollagen I and III showing up in the skin. And after twelve weeks, facial wrinkles were visibly reduced.

Retinoids more broadly stimulate the skin's synthesis of hyaluronan and other glycosaminoglycans, part of what gives skin a plumper, more hydrated look over time.

So even the gentler OTC form is doing real structural work (not just sitting on the surface).

It's also worth knowing Retinol isn't only a wrinkle ingredient; it can help with uneven tone, dark spots, rough texture, and the look of pores as well because it speeds up turnover and influences pigment.

The research backs this up as well.

A pooled analysis of six clinical studies found that 0.1% stabilized retinol improved all signs of photoaging versus vehicle as early as week 4 and through 12 weeks, with only a few mild cases of irritation.

Another study comparing concentrations found that 0.3% and 1% Retinol were similarly effective at remodeling photodamaged skin, but 0.3% caused fewer adverse reactions when used daily (a useful reminder that more isn't always better).

Retinol is about tenfold less potent than Retinoic Acid. This is why it works as a gentler, non-prescription option that builds results over time.

Typical concentrations range from 0.1-1%, with 0.1% to 0.3% being a well-supported sweet spot for visible benefits with good tolerability.

One quirk worth mentioning: Retinol is famously unstable.

It's highly sensitive to light and oxygen, and UV exposure breaks it down into a range of degradation products.

Real-world testing bears this out, with retinoid content in some products dropping anywhere from 0% to 80% after six months at room temperature, and even more at higher temperatures.

This is why good formulations lean on opaque, air-tight packaging (think tubes and pumps, not clear jars) and often "encapsulate" the Retinol to shield it.

Signs of oxidation include your product turning yellow or smelling "off". Keeping it somewhere cool and dark, and using it up within a few months of opening helps it stay effective.

The most common side effects are mild and temporary: usually some dryness, redness, or light peeling as your skin adjusts. These tend to settle with consistent and lower-frequency use.

Like all retinoids, Retinol works best with nightly use, a good moisturizer, and daytime sunscreen.

The "ramp up" method works well: start with Retinol once a week to give your skin time to adjust, which keeps irritation low. Slowly add more nights until you reach your goal frequency once your skin feels comfortable.

Retinoids also make your skin more sensitive to the sun in the first few weeks, so wear sunscreen every morning and protect your skin from direct sun while you build up tolerance.

One safety note: topical Retinoids aren't recommended during pregnancy or breastfeeding. Systemic absorption from creams is low but because high oral vitamin A is a known teratogen and topical safety data are limited, most clinicians recommend stopping retinoids when pregnant or trying to conceive.

In practice, that translates to a long shelf life and a consistently elegant skin feel.

While there is an assumption Caprylic Triglyceride can clog pores due to it being derived from coconut oil, there is no research supporting this. Just patch test if you have concerns.

Fractionated coconut oil and MCT Oil are both listed as Caprylic/Capric Triglyceride according to INCI. This is because INCI names are based on the ingredient’s final chemical composition and not its marketing name or source.

This ingredient is treated as the gold standard fungal acne safe oil. Even though it is coconut derived, the problematic lauric acid is stripped out.

This leaves just caprylic (C8) and capric (C10) acid. These chain lengths actually trend antifungal; a 2020 study found caprylic acid was enough to disrupt Malassezia furfur cell membrane, with a caprylic acid derivative damaging membrane structures at concentrations as low as 0.2%.

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.

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.

Once applied, this ingredient dries down quickly and leaves a dry, silky finish behind. This also helps improve spreadability and texture.

This ingredient has an excellent safety-record and is non-irritating.

Typical concentrations for cosmetics range from 0.5-62%.

Research on Malassezia growth found no growth on fatty acid esters with chain lengths shorter than 12 carbons (it prefers C11-24).

Since Coco-Caprylate/Caprate is built on C8 and C10 fatty acids, it is out of the range that Malassezia metabolizes, and therefore safe for fungal acne.

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.

In Chinese traditional folk medicine, Scutellaria Baicalensis Root Extract is used to help treat lung issues and hypertension.

PHAs are more gentle than AHAs due to their larger structure. They do not penetrate as deeply as AHAs and take a longer time to dissolve dead cells. Studies show PHAs do not cause as much irritation.

Gluconolactone has some interesting properties:

In a 2004 study, Gluconolactone was found to prevent UV damage in mouse skin cells and has not been found to increase sun sensitivity. However, we still recommend wearing SPF daily.

This ingredient is is an created by reacting gluconic acid with an alcohol.

Sodium benzoate works as a preservative by inhibiting the growth of bacteria inside of cells. It prevents the cell from fermenting a type of sugar using an enzyme called phosphofructokinase.

It is the salt of benzoic acid. Foods containing sodium benzoate include soda, salad dressings, condiments, fruit juices, wines, and snack foods.

Studies for using ascorbic acid and sodium benzoate in cosmetics are lacking, especially in skincare routines with multiple steps.

We always recommend speaking with a professional, such as a dermatologist, if you have any concerns.

A 2024 review found evidence for the Rosa canina species supports its use for scarring, hyperpigmentation, wrinkles, and atopic dermatitis; this was mostly credited to its vitamin C content and fatty acid composition as the primary active mechanisms.

You might see this ingredient marketed as a "natural retinol". Some rosehip seed oils contains traces of all-trans-retinoic acid but these trace amounts are far below biologically active levels.

The Cosmetic Ingredient Review Panel has deemed this ingredient safe and it's well-tolerated.

Fungal acne: The fatty acids of this oil fall into the C11-24 range that Malassezia yeast can metabolize, so this ingredient may not be fungal acne safe.

Studies show SAP has anti-acne and antioxidant benefits. One study found 5% of SAP lotion to be an effective ingredient for treating acne vulgaris. This is because research shows that SAP may help control acne by reducing acne-causing bacteria and slowing the oxidation of skin oils caused by UV exposure.

In addition to acne, vitamin C is important for skin structure. Lab studies suggest SAP may support collagen production in skin cells, making it a great ingredient in anti-aging routines.

Vitamin C has many benefits: it helps reduce redness, improve skin texture, fade the appearance of dark spots, and brighten the skin.

Read more about other types of Vitamin C:

Other contents of chondrus crispus include polysaccharides, peptides, and amino acids. These help hydrate the skin.

What's the difference between algae and seaweed?
Algae is a broad term that includes seaweed. Not all algae is seaweed.

A follow-up clinical trial found that a topical crosslinked HA serum applied after fillers, microneedling, or chemical peels was well-tolerated and enhanced skin quality at 14 / 28 days.

More recent research suggests that concentrations as low as 0.03% can act as a penetration enhancer for other skincare actives.

On the safety side, the Cosmetic Ingredient Review Expert Panel has concluded this ingredient to be safe as used in current cosmetic practices + concentrations.

Typical use levels in a formula run about 1-5%.

The skin's ability to produce ceramides gets disrupted in skin conditions like eczema. This in turn weakens the skin barrier and applying ceramides topically has been shown to replenish what's been lost to restore barrier function.

Most of the studies with Ceramide AP test it as part of a multi-ceramide complex; studies reinforce ceramide AP's role in rebalancing ceramides in skin and improving skin hydration.

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.

Xanthan gum is a pretty common and great ingredient. It is a natural, non-toxic, non-irritating ingredient that is also commonly used in food products.

As an antioxidant, it helps fight free-radical molecules. Free-radical molecules are capable of damaging our cells and other genetic material. Thus, antioxidants may reduce the signs of aging.

This ingredient is oil-soluble.

Your skin has a natural pH and acid mantle. This acid mantle helps prevent harmful bacteria from breaking through. The acid mantle also helps keep your skin hydrated.

"Alkaline" refers to a high pH level. A low pH level would be considered acidic.