AHA, BHA, Retinol, Niacinamide & Vitamin C: What Do They Actually Do?

A Beginner-Friendly Guide to Skincare Actives

You've probably seen these names hundreds of times.

AHA. BHA. Retinol. Niacinamide. Vitamin C. Hyaluronic Acid.

But knowing the ingredient name isn't the same as understanding when—or why—you might use it.

Here's the simple version.

AHA — Surface Exfoliation

Alpha hydroxy acids exfoliate the skin's surface.

Glycolic acid is one example.

The Ordinary Glycolic Acid 7% Exfoliating Toner is an AHA-based exfoliating product. The brand recommends applying it no more than once daily, ideally in the evening, and warns against using it on sensitive, peeling or compromised skin. The Ordinary

Think:

AHA → surface texture + dull-looking skin

BHA — Congestion & Blemish-Prone Skin

The BHA you'll see most often in skincare is salicylic acid.

It is particularly associated with products targeting congestion and blemish-prone skin.

The Ordinary Salicylic Acid 2% Solution is one example in the CarifySerums selection. The Ordinary

Think:

BHA → clogged pores + blemishes + congestion

What About AHA + BHA Together?

This brings us to one of The Ordinary's most recognizable products:

AHA 30% + BHA 2% Peeling Solution.

Don't let social media convince you that stronger always means better.

This is a high-concentration exfoliating treatment intended for experienced acid users, according to The Ordinary. The brand instructs users to apply it to clean, dry skin, use it only once or twice weekly, and leave it on for no longer than 10 minutes. It should not be used on sensitive, peeling or compromised skin. The Ordinary

That last point matters.

Skincare isn't a competition to see how much exfoliation your face can tolerate.

Vitamin C — Antioxidant + Brightening Support

Vitamin C is commonly used in morning skincare routines because of its antioxidant properties and ability to support brighter, more even-looking skin.

For example, CeraVe Skin Renewing Vitamin C Serum contains 10% pure L-ascorbic acid. CeraVe says the formula helps visibly brighten the complexion and improve the appearance of fine lines, dark spots and uneven tone. CeraVe

Think:

Vitamin C → antioxidant support + radiance + uneven-looking tone

Niacinamide — The Versatile One

Niacinamide, a form of vitamin B3, has become popular because it can fit into many different skincare routines.

One product you'll find at CarifySerums is:

The Ordinary Niacinamide 10% + Zinc 1%

Rather than thinking of niacinamide as an aggressive corrective treatment, think of it as an ingredient that can complement a balanced routine.

Retinoids — When Your Goal Is Skin Renewal

Retinoids are a major category of vitamin A derivatives.

They're commonly associated with routines focused on signs of aging, texture and skin renewal—but they should be introduced thoughtfully rather than treated like an everyday beginner ingredient from day one.

Your CarifySerums range includes products such as:

The Ordinary Retinol 0.5% in Squalane

and the eye-area treatment:

Beauty of Joseon Revive Eye Serum: Ginseng + Retinal.

If you're new to retinoids, gradual introduction and careful adherence to the manufacturer's directions are important.

Hyaluronic Acid — Hydration Support

Despite having “acid” in its name, hyaluronic acid isn't an exfoliating acid like glycolic or salicylic acid.

It's used primarily for hydration.

That's why a product such as The Ordinary Hyaluronic Acid 2% + B5 belongs in an entirely different category from The Ordinary's exfoliating acids.

Think:

Hyaluronic Acid → hydration

The Rule Worth Remembering

Don't choose an active because it's trending.

Choose it because its purpose matches your skin concern.

And when you're using exfoliating acids, sun protection becomes especially important: The Ordinary specifically warns that its AHA/BHA products can increase sun sensitivity and advises sunscreen, protective clothing and limited sun exposure during use and for a week afterward.