I have a confusion about retinoids that I haven't been able to find an answer to:

If retinoids are approximately vitamin A, does this just mean that the average person is very vitamin A deficient? Should they just be eating vitamin A instead? (The best source is probably animal liver.) Surely this would have not just the beneficial skin effects but also lots of other positive effects on the body (surely facial skin is not the only part of the body bottlenecked by vitamin A).

I wonder if people who eat/absorb lots of vitamin A don't get any marginal benefit from retinoids.

Btw I'll pay $30 for a satisfying answer to this

Clarification: By vitamin A, I literally mean vitamin A. The compound that can be used without conversion. For example, the compound that is consumed through animal sources like liver. 

This is not a good post. I knew that as soon as I saw the title, because there are several different "retinoids" that are very different. Most of them have side effects and a mechanism of action that indicates negative long-term effects. Also some are teratogens. Maybe just read the wikipedia pages for the individual compounds.

The post specifically mentions adapalene which works by "increasing cell turnover" which long-term is presumably a bad thing. It also reduces "keratinocyte differentiation and decrease keratin deposition" which makes skin more fragile, and it increases sensitivity to UV light.

After checking out Melissa55’s YouTube channel, probably worth noting she was on HRT from her 40s until recently, so that might confound the retinoids effect for her in particular.

Anecdotally*, IPL/laser therapy seems to do all of these except increasing  dermal capillaries, which it instead reduces. This makes it ideal for people with rosacea or other inflammatory problems, and fair skin (which often accompanies these problems). 

*And with a few references: Effective treatment of rosacea using intense pulsed light systems - PubMed (nih.gov)
IPL irradiation rejuvenates skin collagen via the bidirectional regulation of MMP-1 and TGF-β1 mediated by MAPKs in fibroblasts - PubMed (nih.gov)
some studies find no significant effect on collagen etc.; I don't know what went wrong here besides perhaps too-tan skin: Intense pulsed light photorejuvenation: a histological and immunohistochemical evaluation - PubMed (nih.gov)

Also, sunscreen has substantial anti-aging benefits of its own so it’s a good idea anyways.

The human body uses the amount of UV light it gets to decide how much of the sex hormones to produce.

I notice substantial positive effects from my habit of getting 20 to 30 minutes of strong sun on my bare arms and legs and eyes every other day. The main positive effect is to make me more optimistic and maybe willing to expend effort and endure suffering in pursuit of my goals. (Naturally I avoid getting more UV than I need to keep my sex-hormone levels high.)

People on this site tend to be too dismissive of seemingly-mild interventions like sunlight. "If the goal is to raise the levels of the sex hormones, why not inject the hormones directly?" they might say. Well, I injected testosterone for a couple of years (decades before I started the habit I just described), and I prefer the effects of the sunlight habit I just described to the effects of injected testosterone. The injected testosterone got me into at least one physical altercation and made me expend much too much time and mental energy in the focused intellectual pursuit I was interested in at the time (programming-language design) and had other negative effects (on general metabolism) that are hard to describe.

Most interventions available to us into the functioning of the central nervous system are too strong in my experience, and injected testosterone's effect on me was too strong. I have a simple model of the brain or at least that part of the brain that controls physiology and mood as consisting of dozens of interlocking feedback loops, and things like injected testosterone alter the equilibrium of too many of the loops too strongly.

Maybe a person wearing sunscreen or high-SPF clothing that covers their arms and legs can get enough UV light to keep sex-hormone levels high through the eyes (as long as they're not wearing sunglasses) but if so, it would require spending at least 2 or 3 times more time in the sun, which makes it less convenient to maintain a habit of UV exposure to keep sex hormones high.

Anyone else getting "ask your doctor if Photoshop™ is right for you" vibes from some of those before & after photos?

Hi Gene! As a fellow research-based skincare enthusiast, I’m thrilled to see this discussion here.

I've been using adapalene for about two years now, and I've experienced all the benefits it's known for: a dramatic improvement in my skin texture, brightness, and acne.

Adding to the sun protection advice, I think this point is so often emphasized in conjunction with retinoids because reversing signs of skin aging is a major motivation for people using them, and UV radiation is a major factor in breaking down collagen and elastin, accounting for up to 80% of skin aging — this figure is cited by both the Skin Cancer Foundation and the American Academy of Dermatology. While retinoids can help reverse some sun damage, it's smart to prevent the primary cause of degradation in the first place. In addition to sun avoidance, I highly recommend Korean sunscreens for their advanced cosmetic technology and comfortable textures, and many of them are very reasonably priced.

Lastly, you shouldn’t use Retinoids if you’re pregnant or likely to become pregnant.

This needs more emphasis. Retinoid signaling is very important for embryonic development, so excess retinoids will really mess up your baby. 

Sharing my experience here:

• VERY white skin, prone to dryness.
• Had been on a cleanser+moisturizer combo before going to sleep for most of my adult life. Very liberal use of sunscreen.
• Came across some research on different retinoids, started with a medium strength retinol serum (The Ordinary 0.5% Retinol Serum in Squalane) before moving to a higher strength retinol serum (The Ordinary 1% Retinol Serum in Squalane). Three drops on a dry skin after using a cleanser, one to each cheek, one to my forehead, spread evenly. Moisturizer applied after letting it settle for around 10 minutes.
  • I chose a cheap product ($9.99) because by default I'm quite distrustful of the beauty industry, and assume that simple and cheap is probably good as long as it has the active ingredient that I want.
    • I chose to start with the 0.5% strength and not the 0.25% for the same reason. My skin was kind of irritated for the first few days, but could handle 0.5% just fine. I moved to 1% in around 1.5 months after using 0.5% daily.
• After roughly six months of using a retinol serum, I moved to a prescription tretinoin cream. Retinol already had quite a big effect, and I'm not sure using tretinoin is that big of an additional difference, at least for me. I do find using a cream easier than a serum, though.

I tend to favour simple and cheap products that have an active ingredient that have at least some amount of research backing up its effectiveness, and that are often recommended by dermatologists. Fancier and expensive products seem like snake oil to me, but I could be wrong on this. My intuition is that less products and less chemicals on your face is probably better than more, and I am quite suspicious of the lengthy multi-step regimens some people subscribe to.

I currently use the following:

• Before going to bed:
  • CeraVe Hydrating Facial Cleanser. Comes in a nice pump. I really love how clean it makes my skin feel.
  • Prescription tretinoin cream.
  • CeraVe Moisturizing Cream. I chose the tub because it was cheaper per mL. Quite thick, good for dry Winters. They also have a lighter feeling ones, but this is good for my current dry climate and skin prone to dryness.
• After waking up:
  • SPF 50 sunscreen. Re-apply around mid-day.
    • If you are able to access them, Japanese and Korean sunscreens are amazing. Can't recommend them enough. They feel like you are not even wearing sunscreen. Leagues and miles ahead of Western sunscreens. This is apparently due to regulatory issues, and the fact that Westerners often ignore the instruction to re-apply sunscreen after a few hours of wear, which has incentivized Western sunscreen manufacturers to optimize for longer lasting (and slimier) sunscreens. Any time friend goes to Japan I tell them to bring me a huge supply of Bioré UV Aqua Rich SPF 50 sunscreen, which is really expensive in the West ($15-30), but really cheap in Japan (like, $4).
    • I am not sure if you actually need to have sunscreen during days which have a relatively low UV index, but all the recommendations say you need to use sunscreen if you are using a retinol or tretinoin product, so maybe there is a reason for that. I tried researching the reason why your skin might be more susceptible to damaging itself, but didn't find anything that seemed obviously correct or applicable to topical use of retinol or tretinoin to me.

I felt a bit validated when I saw that Bryan Johnson also uses CeraVe products, heh.

I change my sheets often, so I tend to skip using a cleanser in the morning due to laziness. If you don't change your bedsheets at least once a week, you might want to do cleanser in the morning as well.

While we're on the topic of skincare, skin can be very individual in how it reacts to things. I have always had crazily fussy skin and the thing that finally helped a lot after two decades of trying different things was snail mucin. Worth a shot if you've never heard of it and have issues. Some people are allergic to it so best to try a drop on your wrist or whatever.

Note that you have to use at least SPF50 sunscreen every day, including during winters, including when it’s cloudy (clouds actually don’t reduce UV that much) if you use tretinoin.

The linked sunscreen is SPF 45, which is not suitable if you’re using tretinoin.

(I used tretinoin for five years and it has had a pretty awful effect on my skin- it made it very shiny/oily. It’s unclear how reversible this is. At some point I learned that it’s a side effect of tretinoin and mostly stopped using it. Some people want their skin to look like that and go for tretinoin to achieve it; for me, it looks pretty unnatural/bad and I am very much not unhappy about it.)

Came across this site on x on my quest for skincare products/ingredients that can help with my extreme soft skin. I have a rare form of soft skin and it’s flappy was wondering if Tretinoid could help firm it up. Also why is it only applied on the face?

Any idea how to get Trentinoin in countries other than the US (e.g. france)?

Not a critique of retinoids but your post is not extremely convincing, I've looked into anti-aging anti-wrinkle cosmetics and the world of products is filled with marketing speak. Reading your post it seems no different from frontpage Google blogs for retinoids or skincare or supplements. Seeing those before and after pics is surprising on a site that loves talking about RCTs and statistical power! But it's hard I'd like to challenge anyone to try googling "vitamin C wrinkles" and see if you can make a conclusion or understand which form or preparation is most effective if at all. Niacinamide, Ha, Ginseng, squalene, vitamins, caffeine... they can't all work can they?

Cosmetics/health stuff marketing is the name of the game here, just slap a bunch of cheap actives into a bottle and your brand and budget will carry you.

I was unable to come to firm conclusions or cut through blog spam / marketing speak, I personally chose to go for "peptides" (aka Matrixyl, matrikines).

• It has been studied to aid wound healing. And this study in Molecular Pharmaceutical, a journal on drug delivery instead of skincare/aging/cosmetic, seems proper https://pubs.acs.org/doi/abs/10.1021/mp300549d
• The first Matrixyl 3000 is patented/licensed by it's inventors (Sederma/Croda), which makes me believe it's 'moat' is its efficacy/trade secret compared with large cosmetics companies who's competive advantage are marketing/brand. The are a ingredients supplier to these companies, since they are B2B they aren't in the marketing game. There are also several similar newer competing 'peptides' that companies have spend R&D on
• For an active ingredient, it doesn't seem the trouble to make compared to many of the simpler ones if it didn't work. It's a triple amino acid that is later palmitoylated to increase topical absorption. That's is just a guess of course, but Palmitoylated-KTTKS doesn't roll off the tongue or look nice on a bottle

Even though they are licensed, they arent much more expensive than high end products with cheaper/ineffective actives. Anecdotally, my skin feels more supple. I have no idea which of the peptides works best

Just a detail : Haven't retinoids been discovered when looking for cancer treatments? I thought it was the origin story behind isotretinoin.

Thanks, this is interesting

I was wondering, do retinoids work as an acute treatment as well? I sometimes have annoying acne spots in various places, but I don't feel like preventatively slathering my whole body in the stuff

Are you afraid of dry eyes/meibomian gland dysfunction at all? It seems like it's pretty common as a side effect of retinoids.

If you would like to buy Differin gel in a country where it is not over the counter such as the UK, you could buy it on iHerb. It is a US site which ships to other countries, I got some Differin gel from there shipped to the UK and it was less painful than figuring out how to get American Amazon or Walmart to ship abroad. But it is more expensive than the Amazon link OP provided, so I guess this is more of a thing if you want to try some out and see if it works for you with as few effort as possible (although beware that it doesn't work immediately, you will probably have to wait a couple months to start seeing results).