Retinol Sleep Serum
Ingredients overview
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Key Ingredients
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Skin Physics Retinol Sleep SerumIngredients explained
Good old water, aka H2O. The most common skincare ingredient of all. You can usually find it right in the very first spot of the ingredient list, meaning it’s the biggest thing out of all the stuff that makes up the product.
It’s mainly a solvent for ingredients that do not like to dissolve in oils but rather in water.
Once inside the skin, it hydrates, but not from the outside - putting pure water on the skin (hello long baths!) is drying.
One more thing: the water used in cosmetics is purified and deionized (it means that almost all of the mineral ions inside it is removed). Like this, the products can stay more stable over time.
A light emollient ester (C8-10 fatty acids connected to C12-18 fatty alcohols) that absorbs quickly and leaves a dry but silky finish on the skin. In terms of skin feel, it is similar to Dicaprylyl Carbonate, another commonly used light emollient.
- A natural moisturizer that’s also in our skin
- A super common, safe, effective and cheap molecule used for more than 50 years
- Not only a simple moisturizer but knows much more: keeps the skin lipids between our skin cells in a healthy (liquid crystal) state, protects against irritation, helps to restore barrier
- Effective from as low as 3% with even more benefits for dry skin at higher concentrations up to 20-40%
- High-glycerin moisturizers are awesome for treating severely dry skin
A little helper ingredient that can boost the performance and enhance the delivery of active ingredients in a formula. It can penetrate deep layers of the skin helping actives to do the same.
It's especially useful to help active ingredients for self-tanning (DHA), anti-acne or skin-whitening to penetrate deeper and work better.
A big molecule from repeated subunits that is used to form gel-like textures and create a film on the skin.
We don't have description for this ingredient yet.
A super common, waxy, white, solid stuff that helps water and oil to mix together, gives body to creams and leaves the skin feeling soft and smooth.
Chemically speaking, it is the attachment of a glycerin molecule to the fatty acid called stearic acid. It can be produced from most vegetable oils (in oils three fatty acid molecules are attached to glycerin instead of just one like here) in a pretty simple, "green" process that is similar to soap making. It's readily biodegradable.
It also occurs naturally in our body and is used as a food additive. As cosmetic chemist Colins writes it, "its safety really is beyond any doubt".
A very common ingredient that can be found in all cell membranes. In cosmetics it's quite the multi-tasker: it's an emollient and water-binding ingredient but it's also an emulsifier and can be used for stabilization purposes. It's also often used to create liposomes.
Hydroxypinacolone Retinoate (HPR) is the newest member of the "royal family of skincare" (see who is who on this cool retinoids family tree), the retinoid family. The queen of the family is the FDA-approved anti-aging superstar, retinoic acid, aka tretinoin and HPR seems to be a gentle but influential sister princess to the queen.
Good to know: the trade name of HPR is Granactive Retinoid. The manufacturer produces it as 10% active and 90% solvent called dimethyl isosorbide. When a product claims 2% Granactive Retinoid, it means 0.2% Hydroxypinacolone Retinoate (and 1.8% dimethyl isosorbide) on the ingredient list.
It's a so-called retinoic acid ester, meaning that it's directly related to retinoic acid. If you've already read our description about retinol or retinyl palmitate, you know that the active ingredient our skin cells can interpret is retinoic acid. Other forms of retinoids have to be converted by our metabolic machinery to do something. That's not the case with HPR. It binds directly to the retinoid receptors of the skin cells to work its skincare magic.
The big promise of HPR is that it's similarly active as retinoic acid (no conversion needed, remember) but without the irritation. According to the manufacturer's tests, 24 hours of an occlusive patch with 0.5% HPR resulted in significantly lower irritation than 0.5% retinol. Also, there was a "dramatic reduction of lines and wrinkles" after applying 0.2% HPR around the eyes twice a day for 14 days.
These results sound sooo promising that we don't blame you if you wanna run out right now and get an HPR formula to slather on your face. But, before you do, you have to know that the info we have about HPR at the moment is mainly from the manufacturer, whose tests may or may not be accurate or properly designed (such as controlled, double-blind and conducted on an appropriate number of people).
As HPR is pretty new there isn't that much independent research we could find yet. We found two Italian studies both examining the efficacy of HPR combined with other things (retinol in both cases, and papain in one of them) for the treatment of acne. Both studies found the formulas effective but they contained other things too, so it's hard to judge how well HPR did.
Regarding anti-aging, there is a pretty recent, Estee Lauder sponsored study that compared the in-vitro (not on real human beings but on skin models) collagen-boosting effectiveness of Hydroxypinacolone Retinoate, tretinoin, good old retinol and retinyl palmitate (RP). The results are pretty encouraging showing that "HPR had greater levels of gene transcription than retinol and RP (RP) at the same concentrations ... however, HPR did not achieve gene transcription levels of ATRA (tretinoin)." But, a much higher dose might be tolerated from HPR and the highest dose of HPR out-performed tretinoin. Pretty encouraging, though we are very much waiting for a study to confirm all this on real human beings.
Bottom line: We are really happy to see some innovation happening with retinoids, and we think Hydroxypinacolone Retinoate is a super promising rising star, but it’s not fully proven yet. If you are someone who likes to experiment and try out the newest things, grab your running shoes and try some HPR containing serum now (see product list below :)). If you like the tried and true, however, stick to retinol and tretinoin for now and re-examine the question in a couple of years when (hopefully) more research will be available.
Are you into Retinoids? Read our shiny description about other members of the retinoid family:
- Retinyl Propionate: the most promising retinol ester out there
- Retinyl Retinoate: a super interesting retinol-retinoic acid hybrid molecule
- Tretinoin: the FDA-proven, well-known active ingredient
- Retinol: the good old vitamin A molecule
- Retinyl Palmitate: a super common, but our least fav member of the retinoids
Unless you live under a rock you must have heard about shea butter. It's probably the most hyped up natural butter in skincare today. It comes from the seeds of African Shea or Karite Trees and used as a magic moisturizer and emollient.
But it's not only a simple emollient, it regenerates and soothes the skin, protects it from external factors (such as UV rays or wind) and is also rich in antioxidants (among others vitamin A, E, F, quercetin and epigallocatechin gallate). If you are looking for rich emollient benefits + more, shea is hard to beat.
A very common water-loving surfactant and emulsifier that helps to keep water and oil mixed nicely together.
It's often paired with glyceryl stearate - the two together form a super effective emulsifier duo that's salt and acid tolerant and works over a wide pH range. It also gives a "pleasing product aesthetics", so no wonder it's popular.
It’s the - sodium form - cousin of the famous NMF, hyaluronic acid (HA). If HA does not tell you anything we have a super detailed, geeky explanation about it here. The TL; DR version of HA is that it's a huge polymer (big molecule from repeated subunits) found in the skin that acts as a sponge helping the skin to hold onto water, being plump and elastic. HA is famous for its crazy water holding capacity as it can bind up to 1000 times its own weight in water.
As far as skincare goes, sodium hyaluronate and hyaluronic acid are pretty much the same and the two names are used interchangeably. As cosmetic chemist kindofstephen writes on reddit "sodium hyaluronate disassociates into hyaluronic acid molecule and a sodium atom in solution".
In spite of this, if you search for "hyaluronic acid vs sodium hyaluronate" you will find on multiple places that sodium hyaluronate is smaller and can penetrate the skin better. Chemically, this is definitely not true, as the two forms are almost the same, both are polymers and the subunits can be repeated in both forms as much as you like. (We also checked Prospector for sodium hyaluronate versions actually used in cosmetic products and found that the most common molecular weight was 1.5-1.8 million Da that absolutely counts as high molecular weight).
What seems to be a true difference, though, is that the salt form is more stable, easier to formulate and cheaper so it pops up more often on the ingredient lists.
If you wanna become a real HA-and-the-skin expert you can read way more about the topic at hyaluronic acid (including penetration-questions, differences between high and low molecular weight versions and a bunch of references to scientific literature).
It's one of the active parts of Chamomile that contains about 30% of bisabolol. It's a clear oily fluid that is used in skincare as a nice anti-inflammatory and soothing ingredient.
A synthetic liquid oil that can replace mineral oil or silicone oils in the cosmetic formulas. There are different grades depending on the molecular weight ranging from very light, volatile, non-residue leaving ones to more substantial, slight residue leaving ones.
Apart from leaving the skin soft and smooth (emollient), it's also used as a waterproofing agent in sunscreens or makeup products and as a shine enhancer in lip gloss formulas.
If you have spotted ethylhexylglycerin on the ingredient list, most probably you will see there also the current IT-preservative, phenoxyethanol. They are good friends because ethylhexylglycerin can boost the effectiveness of phenoxyethanol (and other preservatives) and as an added bonus it feels nice on the skin too.
Also, it's an effective deodorant and a medium spreading emollient.
- It’s the second most researched AHA after glycolic acid
- It gently lifts off dead skin cells to reveal newer, fresher, smoother skin
- It also has amazing skin hydrating properties
- In higher concentration (10% and up) it improves skin firmness, thickness and wrinkles
- Choose a product where you know the concentration and pH value because these two greatly influence effectiveness
- Don’t forget to use your sunscreen (in any case but especially so next to an AHA product)
A type of lipid that's the major (about 75%) component of all cell membranes. As for skincare, it works as an emollient and skin-identical ingredient.
It has a water-loving head with two water-hating tails and this structure gives the molecule emulsifying properties. It is also often used to create liposomes, small spheres surrounded by phospholipid bi-layer designed to carry some active ingredient and help its absorption.
A vegetable-based, PEG-free ingredient whose job is to help water and oil to mix nicely together (emulsifier). It is created by attaching ten water-loving glycerin molecules with the oil-loving fatty acid, stearic acid. The result is a partly water- and partly oil-loving molecule that creates stable and smooth emulsions that are also cosmetically elegant. It also has some moisturizing and softening benefits for skin and hair.
- Retinol (pure Vitamin A) is probably the most proven anti-aging ingredient available OTC
- It has to be converted in the skin to retinoic acid to work its magic
- Once converted, it has the same effect as all-trans-retinoic acid, aka tretinoin
- A generally accepted ballpark number is that retinol is 10-to-20 times less potent than retinoic acid
- It makes skin less wrinkled, smoother, firmer and tighter
- It might also be helpful for acne prone skin as it normalizes keratinization and makes the pores produce less sebum
- Possible side effects and irritation are also much less than with retinoic acid
- Do not use whilst pregnant
Sunflower does not need a big intro as you probably use it in the kitchen as cooking oil, or you munch on the seeds as a healthy snack or you adore its big, beautiful yellow flower during the summer - or you do all of these and probably even more. And by even more we mean putting it all over your face as sunflower oil is one of the most commonly used plant oils in skincare.
It’s a real oldie: expressed directly from the seeds, the oil is used not for hundreds but thousands of years. According to The National Sunflower Association, there is evidence that both the plant and its oil were used by American Indians in the area of Arizona and New Mexico about 3000 BC. Do the math: it's more than 5000 years – definitely an oldie.
Our intro did get pretty big after all (sorry for that), so let's get to the point finally: sunflower oil - similar to other plant oils - is a great emollient that makes the skin smooth and nice and helps to keep it hydrated. It also protects the surface of the skin and enhances the damaged or irritated skin barrier. Leslie Bauman notes in Cosmetic Dermatology that one application of sunflower oil significantly speeds up the recovery of the skin barrier within an hour and sustains the results 5 hours after using it.
It's also loaded with fatty acids (mostly linoleic (50-74%) and oleic (14-35%)). The unrefined version (be sure to use that on your skin!) is especially high in linoleic acid that is great even for acne-prone skin. Its comedogen index is 0, meaning that it's pretty much an all skin-type oil.
Truth be told, there are many great plant oils and sunflower oil is definitely one of them.
A super common emollient that makes your skin feel nice and smooth. It comes from coconut oil and glycerin, it’s light-textured, clear, odorless and non-greasy. It’s a nice ingredient that just feels good on the skin, is super well tolerated by every skin type and easy to formulate with. No wonder it’s popular.
- Primary fat-soluble antioxidant in our skin
- Significant photoprotection against UVB rays
- Vit C + Vit E work in synergy and provide great photoprotection
- Has emollient properties
- Easy to formulate, stable and relatively inexpensive
It’s pretty much the current IT-preservative. It’s safe and gentle, but even more importantly, it’s not a feared-by-everyone-mostly-without-scientific-reason paraben.
It’s not something new: it was introduced around 1950 and today it can be used up to 1% worldwide. It can be found in nature - in green tea - but the version used in cosmetics is synthetic.
Other than having a good safety profile and being quite gentle to the skin it has some other advantages too. It can be used in many types of formulations as it has great thermal stability (can be heated up to 85°C) and works on a wide range of pH levels (ph 3-10).
It’s often used together with ethylhexylglycerin as it nicely improves the preservative activity of phenoxyethanol.
It's the acronym for Butylated Hydroxy Toluene. It's a common synthetic antioxidant that's used as a preservative.
There is some controversy around BHT. It's not a new ingredient, it has been used both as a food and cosmetics additive since the 1970s. Plenty of studies tried to examine if it's a carcinogen or not. This Truth in Aging article details the situation and also writes that all these studies examine BHT when taken orally.
As for cosmetics, the CIR (Cosmetic Ingredient Review) concluded that the amount of BHT used in cosmetic products is low (usually around 0.01-0.1%), it does not penetrate skin far enough to be absorbed into the bloodstream and it is safe to use in cosmetics.
Exactly what it sounds: nice smelling stuff put into cosmetic products so that the end product also smells nice. Fragrance in the US and parfum in the EU is a generic term on the ingredient list that is made up of 30 to 50 chemicals on average (but it can have as much as 200 components!).
If you are someone who likes to know what you put on your face then fragrance is not your best friend - there's no way to know what’s really in it.
Also, if your skin is sensitive, fragrance is again not your best friend. It’s the number one cause of contact allergy to cosmetics. It’s definitely a smart thing to avoid with sensitive skin (and fragrance of any type - natural is just as allergic as synthetic, if not worse!).
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| what‑it‑does | solvent |
| what‑it‑does | emollient |
| what‑it‑does | skin-identical ingredient | moisturizer/humectant |
| irritancy, com. | 0, 0 |
| what‑it‑does | solvent | viscosity controlling |
| what‑it‑does | viscosity controlling |
| what‑it‑does | emollient | emulsifying |
| irritancy, com. | 0, 1 |
| what‑it‑does | emollient | emulsifying |
| what‑it‑does | cell-communicating ingredient |
| what‑it‑does | emollient |
| what‑it‑does | surfactant/cleansing | emulsifying |
| irritancy, com. | 0, 0 |
| what‑it‑does | skin-identical ingredient | moisturizer/humectant |
| irritancy, com. | 0, 0 |
| what‑it‑does | soothing |
| what‑it‑does | emollient | viscosity controlling |
| irritancy, com. | 2, 1 |
| what‑it‑does | preservative |
| what‑it‑does | exfoliant | moisturizer/humectant | buffering |
| what‑it‑does | skin-identical ingredient | emollient |
| what‑it‑does | emulsifying |
| what‑it‑does | cell-communicating ingredient |
| what‑it‑does | emollient |
| irritancy, com. | 0, 0 |
| what‑it‑does | emollient |
| what‑it‑does | antioxidant |
| irritancy, com. | 0-3, 0-3 |
| what‑it‑does | preservative |
| what‑it‑does | antioxidant | preservative |
| what‑it‑does | perfuming |