Not All Vitamin A Is Created Equal: The Difference Between Retinol, Retinal, Retinoic Acid & Retinyl Esters

Vitamin A (commonly referred to as Retinol) is one of my favorite skincare topics because the terminology gets confusing fast. People hear "retinol," "retinal," and "retinoic acid" used interchangeably, but they're actually different forms of vitamin A that require different amounts of work from your skin in order for them to become biologically active.

The key difference is how many conversion steps your skin has to perform before the ingredient becomes retinoic acid (the only form your skin cells can actually use.)

The Vitamin A Family (Most Active → Least Active)

Retinoic Acid (Prescription)
        ↑
     Retinal (aka Retinaldehyde)
        ↑
      Retinol
        ↑
 Retinyl Esters
 (Retinyl Palmitate, Acetate, Propionate)

1. Retinoic Acid (Prescription)

This is the biologically active form of vitamin A that skin cells actually use.

No conversion is required.

This includes prescription ingredients like tretinoin (all-trans retinoic acid) and other brand names  like Retin-A, Retin-A Micro, Altreno, Alfralin, Refissa, Renova, Avita. Because it's already active, it begins working immediately once it reaches the skin.

Since it bypasses all conversion steps, it's also the most potent (and often the most irritating) form of vitamin A. Works great for those who are already maintaining a strong barrier with something like ETHYST.

2. Retinal (Retinaldehyde)

Only ONE conversion step away from becoming retinoic acid.

Retinal
   ↓
Retinoic Acid

Because only one enzymatic step is required, retinal works relatively quickly and is considered the closest over-the-counter ingredient to prescription retinoic acid.

Benefits include:

• Faster visible results than retinol (not to be confused with retinoic acid)
• Excellent support for acne-prone skin
• Strong collagen stimulation
• Can be less irritating than prescription retinoic acid

One challenge is that retinal is significantly less stable than retinol. It oxidizes more easily, meaning it's much more difficult to formulate and needs to be packaged properly. Additionally, for best results, it's still important to use microbiome-balancing skincare to ensure you are supporting and maintaining a healthy barrier.

3. Retinol

Requires TWO conversion steps to become retinoic acid. 

Retinol
    ↓
Retinal
    ↓
Retinoic Acid

Because your skin must perform both conversions, retinol generally works more gradually than retinal.

Benefits include:

• Stimulates collagen production
• Improves skin texture
• Softens fine lines
• Helps fade discoloration
• More chemically stable than retinal

While retinol has been considered the gold standard among over-the-counter retinoids for decades because it provides an excellent balance of effectiveness, stability, and tolerability, it is a much slower process than using retinoic acid.

4. Retinyl Esters

Examples include:

• Retinyl Palmitate
• Retinyl Acetate
• Retinyl Propionate

These require THREE conversion steps.

Retinyl Ester
      ↓
Retinol
      ↓
Retinal
      ↓
Retinoic Acid

Because the skin has to perform multiple conversions before these ingredients become active, they generally produce less of the initial irritation associated with more biologically active retinoids. However, they're also the least potent members of the vitamin A family.

Retinyl esters are commonly used because they're inexpensive, highly stable, and have a long shelf life, making them attractive ingredients from a cost-based manufacturing standpoint. 

However, lower biological activity doesn't automatically make them the best choice for skin. Many formulators prefer more effective vitamin A derivatives, such as retinol or retinal, because they deliver greater results while still being well tolerated when thoughtfully formulated. 

Ultimately, decades of research continue to support prescription retinoic acid, used alongside a healthy, well-functioning skin barrier, as one of the most effective approaches to long-term skin health and healthy aging.

Why is retinal getting so much attention?

Because it sits in the "sweet spot."

It's only one conversion step away from becoming retinoic acid, allowing it to deliver results more efficiently than retinol while still being available over the counter.

In general, fewer conversion steps mean:

• Faster biological activity
• Greater potential potency
• Less conversion loss before reaching the active form

So...why do some people still prefer retinol?

This is where formulation matters.

Although retinal requires fewer conversion steps, that doesn't automatically make every retinal product better than every retinol product.

A retinoid's real-world performance depends on factors like:

• Concentration
• Formulation quality
• Stability
• Packaging
• Delivery system
• Supporting ingredients

A well-formulated retinol can absolutely outperform a poorly formulated retinal.

Retinol is also inherently more stable than retinal, which is one reason it has remained an industry favorite for so many years.

However, as a Licensed Esthetician and science-based Formulator, my opinion is that the best approach to healthy skin and anti-aging is a combination of retinoic acid, a strong resilient barrier maintained with biological, microbiome-based skincare and daily sunscreen of at least SPF 30. 

This is also why I do not formulate over the counter skincare products with actives. The philosophy of ETHYST® is rooted in stabilizing the biology of the skin because the science shows us that formulations emulating the science of the skin vs. aggressively treating the skin with lower grade external actives is the most effective strategy.

Please note, ensuring your barrier is healthy prior to using retinoic acid will make a world of difference. Think 6-12 months of consistent inflammation reduction and maintenance prior to introducing tretinoin.

An easy way to think about it

Imagine your skin needs to get to the finish line (retinoic acid).

• Retinoic acid starts at the finish line.
• Retinal starts one block away.
• Retinol starts two blocks away.
• Retinyl esters start three blocks away.

The fewer "blocks" your skin has to travel, the more efficiently that ingredient can become biologically active.

Quick Comparison

* Please note that while retinoic acid may officially have the highest irritation potential, this information is based on the average skin barrier and the amount of damage being caused by constant product changes, harsh ingredients commonly found in products, and other factors.

When the skin barrier is resilient and healthy, the irritation potential of a product naturally lessens overall.

The takeaway

Retinoic acid is the most biologically active form of vitamin A because it requires no conversion by the skin. Retinal comes next, requiring just one conversion step to become active. Retinol requires two conversion steps, while retinyl esters require three. Generally, the fewer conversion steps required, the greater the potential biological activity. However, formulation quality, concentration, stability, and packaging all play a major role in how well a product ultimately performs.

One final note: you'll often hear people say that retinal is "stronger" than retinol. A more accurate way to say it is that retinal is closer to the active form, so it has the ability to achieve comparable results with greater efficiency. However, you have to remember, the quality of formulation is critically important. Just because the conversion is closer doesn't necessarily make every retinal product superior to every retinol product.

While over-the-counter retinoids certainly have their place, decades of clinical research continue to point to prescription retinoic acid (combined with a healthy, resilient skin barrier) as the gold standard for long-term skin health and healthy aging.