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  • Writer's picturePenn Smith

Retinoids: so powerful yet so confusing

Updated: Jan 2, 2023

Retinol, Retinaldehyde, Tret and Retin-A, oh my!! Making sense of Retinoids.

If you’re on the anti-aging path, you’ve surely heard of the miracle of retinoids. The term ‘retinol’ has enjoyed a meteoric climb in the realm of internet searches. In fact, there has never been so much interest in retinol as there is today with Google searches up 400% in the past five years(!!!) I credit this to the massive increase in products that include some form of this miraculous Vitamin A derivative - and the massive marketing spend that big skincare brands are putting behind it.

I think this is such a positive thing. The benefits of retinoids cannot be matched in the anti-aging realm. In fact, retinoids have more clinical proof and peer-reviewed studies that attest to their efficacy than any other ingredient out there. And it isn’t just a fly-by-night ingredient - topical retinoids have been studied for over forty years.


Retinoids work by binding with specific receptors in the DNA of skin cells, encouraging faster turnover, and hindering the production of collagenases, enzymes that break the peptide bonds in collagen.

The fat-soluble retinoid molecules penetrate the stratum corneum and, depending on the strength of the retinoid, into the dermis where it does some serious work. By communicating with receptors inside keratinocytes, retinoids promote them to proliferate, strengthen the skin barrier, reduces water loss, and protects collagen from degenerating among other things. All of this stimulation of new collagen production and tightening/rearranging of existing collagen fibers leads to bouncier skin that has fewer lines and reflects light in a more youthful way. You’ve heard me talk about ‘tyrosinase inhibitors’. Well, studies show that retinoids reduce tyrosinase activity in melanocytes, helping to address hyper-pigmentation. No doubt about it; retinoids really are the ‘superhero’ of antiaging.

So why aren’t we all using this magic ingredient successfully and looking ten years younger!? I think it's because, while retinoids are the stars of the anti-aging show, they’re also the most misunderstood.


Retinoids are a powerful form of Vitamin A that can have deep and wide-reaching impact on the cellular makeup of our skin. The strongest and most potent form is called Retinoic Acid (aka ‘Tret’ or Retin-A). Like many active ingredients, Retinoic Acid is volatile when exposed to air and light. In addition, because it’s strong it needs to be handled with respect - so requires a doctor’s prescription in most countries. (I find many people are so enthusiastic about Tretinoin that they start strong and then quit because of the sensitivity that can accompany strong Retinoids.)

In an effort to bring the anti-aging effects of Vitamin A to as broad an audience as possible, chemists have created forms of this superstar that are less volatile and more suitable for a broader range of skin types without causing the tell-tale ‘Tret scaling/peeling’. This is great! The problem (as I see it) is in how the industry has named different Retinoid derivatives and educated the public (or not!) on the differences in potency and other features. Read on for clarifications and my recommendations.


In a broad sense, there are two kinds: Active and Inactive. Think of active forms as those that need a doctor's prescription and inactive as the ones you can order on Amazon, Sephora or even buy at your local supermarket. With the inactive forms, your body needs to convert them into the active form in order for them to have an anti-aging benefit. In order of weak to strong, these are the most common forms of retinoids that you’ll see out there (there are too many to name them all!):

The important thing for you to remember is: the closer a form of Retinoid is to Retinoic Acid, the BETTER and FASTER it works.

*Penn Smith Skincare is a participant in the Amazon Services LLC Associates Program, an affiliate program. Many links are affiliate links, meaning I am compensated when you shop through these at no extra fee to you.

1. Non-Prescription (Inactive)

Retinyl esters: These represent the gentlest form of over-the-counter retinoids and are fine for people new to retinoids especially those with sensitive skin. They very stable and have good shelf life. Bear in mind that Retinyl esters need to be converted into retinol, then retinal, and finally Retinoic Acid (where it starts doing the work.) You'll see them listed on labels as Retinyl Acetate, Retinyl Linoleate, Retinyl Palmitate, and Retinyl Proprionate.

Retinol: I find that ‘Retinol’ has become almost synonymous with ‘Tretinoin’ in many circles, even In magazines and from ‘expert sources’. This is perhaps the biggest cause of confusion. Retinol is abundantly available OTC but only has about 1/20 of the strength of Tretinoin (and can still be irritating.) So while it’s a better bet than Retinyl esters in terms of speed of results, there’s a better choice for people with sensitive skin or those concerned with irritation and redness.

Drunk Elephant Retinol (1.0%)

Sunday Riley Luna Retinol (6.5%)

Cos de Baha Retinol Serum (2.5%)

Budget friendly:

Cerave Resurfacing Retinol Serum

Cerave Skin Renewing Retinol Serum

Naturium Retinol Complex Cream

Babyface Night Renewal Retinol Cream

Retinal (a.k.a. Retinaldehyde): This is my preferred form of non-non-prescription retinoids as it is stronger than retinol yet tends to cause far less irritation. I find this works well for beginners and sensitive skin.


Osmosis Renew (0.15%) or Correct (0.075%) (use code penn20 for 20% off)

Avene RetrinAL (0.05%)

Mychelle Retinaldehyde (1.0% yes, I double-checked!!) It contains a special formulation called IconicA® which seems to make it more stable. I'm not sure if the others use this too?®-was-created-first-stable-retinaldehyde-industry

2. Prescription (Active)

Retinoic Acid - Tretinoin (a.k.a Tret): Tretinoin is a potent retinoid that’s available by prescription in most countries. Compared to its drugstore counterparts, it isn’t very stable. Being highly sensitive to light and oxidation you’ll want to keep it tightly closed and away from sunlight. When you hear the term 'gold standard in anti-aging', it's Retinoic Acid that's being discussed. It has HEAPS of clinical data supporting its efficacy and is the ONLY topical treatment that has FDA approval for the treatment of photo-aging. It also provides the quickest results.

Because Retinoic Acid is so strong it can cause peeling, sensitivity, and redness - and this can last for months!! It is vital to talk to your medical professional to determine the best 'starting dose' and 'ramp-up plan' for you. The strength you'll be prescribed depends on a number of factors. Someone with thicker/darker skin who's been using AHAs/BHAs for years may start out with 0.05 whereas a lighter-skinned person with sensitive skin may start out with a 0.025 strength. Unfortunately, some people will be unable to tolerate Retinoic acid (but maybe just fine with Retinaldehyde.) Retinoic acid is generally the most expensive option of the Retinoid family.

Available in strengths 0.025%, 0.05%, and 0.1% from your doctor and in a broader range of strengths (typically mixed with other ingredients) via custom prescription-strength skincare services such as Curology and Dermatica.

Adapalene: is a new generation synthetic retinoid. Adapalene is more stable than Tretinoin, has better absorption ability, and is said to be less irritating.

Differin is a prescription-strength retinoid now available over the counter in the US.  Initially used for acne (Differin touts the ability to clear 87% of acne in 12 weeks) it is now a great alternative to tretinoin for anti-aging!  All the same precautions and timelines should be observed as with Tretinoin.  I personally think it is exciting that a prescription-grade retinoid is available at the drugstore at a crazy-good price (under $20!). 

Bakuchiol: the retinoid that isn’t a retinoid. I'll be doing an entire blog post dedicated to this plant-based Vitamin A alternative!


As a rule, I recommend that people chose a Retinoic acid product that's in the 'middle range' for their skin type. Choose a product that's too mild and you won't see results (and risk quitting!). Choose a product that's too strong and you'll end up with red, scaly skin (and risk quitting!)



Once you've chosen the form of retinoic acid that suits your skin type you'll want to make sure it gets the right slot in your regime. First things first; getting off on the right step:


Assuming you've opted for a 'middle of the strength range' choice (depending on your own skin type), I recommend that you ease in to 'test the waters'. Start with a pea-size amount dotted evenly around your face (some formulations are thick and can be difficult to spread once applied to the face) every 72 hours. Slow and steady wins the race here! I find there can be a lag time between application and reaction/irritation, so you may not know for 3-5 days whether you need to back off a bit. If you do experience irritation in the first week to ten days, simply space out your applications a bit further and observe reactions. If you experience no reaction after a month of using every 72 hours, feel free to apply your retinoid in 48-hour windows.


1. Apply to dry skin after using a pH balanced cleanser and wait 20 to 30 mins. Skin that is slightly damp has higher porosity allowing more absorption, so the wait is worth it to avoid potential irritation.

If you're concerned about stepping up to a more intense retinoid, do feel free to 'buffer' the product by using a moisturizer immediately after you cleanse.

2. Retinoids can make your skin more sensitive to UV rays and sunlight decreases the efficacy of Tretinoin so I recommend most retinoids be used before bed. Retinol may be used during the day as it is not sensitive to the sun but always watch for irritation. If you are using Tretinoin at night using retinol in the morning as well maybe just too much of the vitamin.

3. Apply a pea-sized amount, dotted over the face, and blend evenly avoiding the area immediately around your eyes.

4. Avoid any areas where you have tattoos or permanent makeup as retinoids do such a good job with cellular turnover that they can quickly fade your investment in those defined eyebrows!!


The main concern with combining retinoids with other skincare is irritation. I now use my retinoids last in my nighttime routine to buffer the irritation.

A sample PM routine including retinoids might go like this:

  1. Cleanse

  2. Tone (if you do)

  3. Growth factors (if you do)

  4. Peptides (if you do)

  5. Hydration (could be a serum or moisturizer or both)

  6. Eye cream (if you do)

  7. Pigment Inhibitor (like hydroquinone)

  8. Retin-a (tretinoin) (you can mix this with moisturizer to further the spread of your Retin-a)

A sample AM routine could look like this:

  1. Cleanse

  2. Exfoliate (manual- if you do)

  3. Tone

  4. Vitamin C (I always wait a couple minutes before moving on...this is optional)

  5. AHA/BHA (serum form)

  6. Peptides

  7. Growth Factors

  8. Retinol (if you want, but not if you use tretinoin at night. You can use retinol at night instead of Tret and in that case I wouldn't use it again in the morning. Basically choose am OR pm to use your retinoids with only Tretinoin limited to nighttime)

  9. Hydrators (serums/moisturizer)

  10. Sunscreen

  11. Make-up if you wear it


Clearista is a keratin dissolver and one of my favorite gentle exfoliators. It dissolves the skin flakes with no irritation. It is quite alkaline so be sure to follow it up with a toner that will bring your skin back to 4.5

Theraderm. is one of my favorite enzyme products.

Be wary of harsh scrubs and high AHAs. Prolonged inflammation is pro-aging.



Use code Penn for 20% off


1. How do I tell which is stronger: for example 2.5% retinoid or a 0.5 Tretinoin? Because the retinol is inactive and requires an enzymatic process to convert in to tretinoin it is not as strong but might be equally irritating. Remember that retinol is 20X weaker than tretinoin (said another way: Tretinoin is 20X stronger than retinol).

2. How long before I'll see any changes? Typically changes take 6-9 months to begin to show. Often positive changes take a year but will continue after that.

3. I'm still confused. Which is your favorite Penn? My favorite is Tretinoin. After that retinaldehyde.

4. At what age should someone start Retinoids?

Personally I think that about 28 is a great age to start the preventative use of retinoids. Prior to that retinoids may be used of course to treat specific skin conditions like acne.

5. Which is the best Retinoid to use if I have rosacea or sensitive skin? Retinaldehyde

6. I've heard that Retinoids can make the skin thinner and actually contribute to wrinkles over time. Is this true? Retinoids actually thicken the dermis-the layer of skin that is responsible for most wrinkle formation.

7. Can Retinoids be used around the eye area? There are eye creams formulated with retinol that can be very effective at wrinkle correction and prevention. Always take care when putting any active around the eye. Rule of thumb is to gently pat eye cream in on the ocular bone. Let circulation do the rest:).

8. I've heard that it's best to 'cycle' Retinoids - six months on and six months off. Is this true? I suggest using a retinoid year-round while being diligent with sunscreen.

I hope that this blog was helpful and I also hope it finds you safe and healthy.

Take care,


FTC: Links in this post are affiliate ~ Please note that all links on this page are affiliate and I participate in the Amazon Associates program which is an affiliate program. Any time you see an Amazon link it is affiliate. If you choose to use my links please know that I appreciate it!

Disclaimer: This post is not intended to provide diagnosis, treatment or medical advice. Content provided on this blog is for informational and entertainment purposes only. Please consult with a physician or other healthcare professional regarding any medical or skin related diagnosis or treatment options. Information on this website should not be considered as a substitute for advice from a healthcare/skin professional. The statements made about specific products throughout this website are not to diagnose, treat, cure or prevent disease. It is important that you check labels to determine if a product is right for you. Before starting any treatment at home consult a health care or skin care professional to determine if it’s right for you.

18,156 views8 comments

8 comentarios

15 feb 2023

hello. can you use red light therapy while using tretinoid?

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María Marty
María Marty
11 oct 2021

Thank you for this article. My question is: Can you combine Retin A and microneedling or it´s not convenient? If you can, how many days you have to wait after microneedling to use Retin A? Thanks! .)

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Paula Yong
Paula Yong
07 may 2021

Thank you so much. This is so incredibly helpful for me. A noob with tret!

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Patty Yu
Patty Yu
18 mar 2021

I have just seen your video about NIOD products. Please guide me :

If I am just starting to use retinol ( I just bought few of the A group, one with B3, one just treatment ) Also, I earned from website that starting of 2 night a week.

Anyway, my question is : can we mix NIOD your favourite serum ( Multi Molecular Hyaluronic complex and Copper Amino isolate serum ) with Retinol products ?

Please let me know .

Thank you so much

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Jessica Leslie
Jessica Leslie
16 nov 2020

I see in this sample list you have it written that we can use an aha serum after our vitamin c so we can still use our vitamin c daily?? What is a good aha serum you would recommend?

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