Don't believe the claim that retinol is the same as a retinoid,

Don't believe it

Director Wi Young-jin of Beauty's Doctor · Former Seoul National University specialist

Check this before you read

Q. Aren't retinol and retinoid basically the same thing?

A. No. Both are vitamin A derivatives, but

the way they pass through the stratum corneum is completely different.

So the irritation and the results are different too.

Q. Why is it that even though they're both vitamin A

the concentration and strength vary so much?

A. Because the skin's stratum corneum acts as a 'gate'.

The key is how it passes through that gate.

Key points of this article

Retinol, retinoid, tretinoin,

the reason concentrations and strengths differ is the stratum corneum.

What is a retinoid?

Retinoid (Retinoid) is an umbrella term for vitamin A

and its derivatives.

In simple terms, retinol is a retinoid, and

tretinoin is also a retinoid.

But here's the part many people misunderstand:

you can't put an equals sign between

'retinoid = retinol'.

Retinoid is the 'family name',

and retinol, retinal, and tretinoin are the

'individual names' within that family.

The differences among these individuals are

much bigger than you might think.

And the key factor that creates those differences

is the stratum corneum.

The real reason concentrations and strengths differ

— the gate called the stratum corneum

At the very outermost layer of the skin is a

very thin protective barrier called the stratum corneum.

It's only about 0.01~0.02mm thick,

and this thin layer blocks most external substances.

That is its role.

This means that even good ingredients for the skin must

pass through this stratum corneum to reach the dermis.

Retinol passes through the stratum corneum and then

undergoes two conversion steps inside the skin.

Retinol → retinal → tretinoin (retinoic acid)

The active form that ultimately acts on skin cells is

tretinoin.

Each time retinol is converted, some of its potency is lost.

Absorption also drops as it passes through the stratum corneum,

and conversion efficiency varies from person to person.

By contrast, tretinoin is already the active form itself.

No conversion process is needed.

Even though both are vitamin A, retinol 0.5% and

tretinoin 0.025% are not comparable in terms of

strength.

Director Wi Young-jin's key summary

Retinol must pass through the stratum corneum

and go through two conversions to be effective.

Tretinoin works immediately without conversion,

so it's faster, but also more irritating.

Which form is right for your skin

depends on the state of your skin barrier.

Retinol vs retinal vs tretinoin comparison

Guidance by case

1. Who should start with retinol

If you're new to vitamin A ingredients,

or have thin, sensitive skin.

Start at around 0.1~0.3% and gradually increase.

2. Who can move on to retinal

Those who have used retinol 0.5% or more

for over 3 months without any problems.

You'll notice the effects much faster.

3. Who needs tretinoin

Those who actively want to improve acne scars, deep pigmentation,

and wrinkles.

You must get a prescription.

For tretinoin, the initial 2~3 weeks are really tough.

If you get through the peeling and stinging phase,

you can see improvements in skin tone and elasticity.

3 things you must follow when using retinoids

1. Sun protection is absolutely essential

As the stratum corneum becomes thinner, the skin becomes more vulnerable to UV rays,

so you must apply sunscreen with SPF 50 or higher.

2. Moisturize first, retinoid on top

If you're a beginner, I recommend the

'sandwich method' of layering retinoid over moisturizer.

3. Don't use it every day at first

Start 2~3 times a week, then move to every other day once you adapt,

and then daily use; that's the safest approach.

Frequently asked questions

Q1. Can I switch directly from retinol

to tretinoin?

The irritation is strong. Take about a week off retinol, then

start tretinoin at the lowest concentration, twice a week.

Q2. How long do I need to use it to see results?

Retinol becomes noticeable after 8~12 weeks, and tretinoin after 4~8 weeks,

but wrinkle improvement requires

consistent use for over 6 months.

Q3. Does using retinoids thin the skin?

That's the most common misconception. The stratum corneum may thin, but

the dermis becomes thicker as collagen synthesis is promoted,

so in fact it thickens.

WhatsApp consultation before your visit is also available.

This has been Wi Young-jin.

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