Vitamin C or AHA: which one for your skin?

Two acids that promise the same radiance, through opposite mechanisms. Vitamin C acts on pigmentation and protects against free radicals. AHAs remove dead surface cells. One corrects color, the others texture.

What separates them

What Vitamin C does

It neutralizes some of the free radicals produced by exposure and pollution, acts on dark spots and evens out skin tone. Vitamin C also acts as a cofactor in collagen production.

It is available as ascorbic acid — the most effective and demanding form — or as stabilized derivatives, which are gentler and slower. For reactive skin, the latter option is well worth it.

What AHAs do

Alpha-hydroxy acids are water-soluble and act on the surface. Glycolic acid is the most penetrating, while lactic acid is the gentlest.

They detach accumulated dead cells, which improves radiance and refines skin texture in two to three weeks — significantly faster than vitamin C.

Their drawbacks are twofold: they can be drying and significantly increase sensitivity to sunlight.

Which one to choose

Dark spots, irregular pigmentation: Vitamin C, the only one of the two to act on color.

Dull complexion, uneven skin texture, fast results: an AHA.

Sensitive skin: Vitamin C in a stabilized derivative, or lactic acid used very sparingly.

Both: This is the most common case, and the combination works well if applied at different times.

The separation that solves everything

Vitamin C in the morning, AHA at night. This routine avoids combining acids in a single application and respects the time when each is most beneficial.

Vitamin C is used during the day when the skin is exposed to radiation. AHA works at night, and its photosensitizing effect is not compatible with daytime exposure.

If you need to layer them

This is possible but not highly recommended for beginners. Apply AHA to clean, dry skin, wait a full ten minutes, then apply vitamin C and a cream.

Never reverse the order: a serum applied first would form a film that would hinder the acid's action on the surface.

Adding a humectant

A hyaluronic acid serum applied to damp skin makes this routine significantly more comfortable, especially on exfoliation days.

Neither vitamin C nor AHAs provide moisture. This is the most cost-effective and often overlooked addition.

Progression, week by week

Weeks 1 and 2: Vitamin C only, every morning.

Week 3: Add AHA once a week, at bedtime.

Week 5: Twice, if no dryness occurs.

After that: A maximum of three times.

Sun protection, non-negotiable

AHAs significantly increase sensitivity to UV rays, and vitamin C loses its effectiveness if you don't protect what it helps preserve. Daily sun protection is essential for the results of both.

For spots in particular, unprotected sun exposure can undo in a few weeks what three months of routine have built.

Adding hyaluronic acid

This is the most beneficial supplement to both. Hyaluronic acid replenishes the water that AHA removes from the surface and softens the sensation that vitamin C can leave.

Applied to damp skin before the active ingredient, it does not interfere with either. The three can be layered without difficulty.

On sensitive skin

A stabilized vitamin C derivative, and lactic acid once a week at most. Glycolic acid should be avoided until tolerance is established.

If your skin reddens easily, start with a month of soothing treatments only — panthenol or ceramides — before introducing any acid.

What each does not do

Vitamin C does not exfoliate and does not affect surface texture. AHA does not act on pigmentation: it only accelerates the removal of cells containing it.

Neither provides lipids. A cream is still necessary, and even more so on exfoliation days.

How to apply them

A serum is applied to clean skin, a few drops distributed with fingertips. Applying more does not improve anything: the skin only absorbs what it can.

The gesture is as important as the product. Pat rather than spread, let it penetrate for one minute, then seal with a cream. This last step conditions the hydration achieved.

Reading an ingredient list

Ingredients appear in descending order of quantity. An active ingredient listed at the end of the list, after preservatives, is present in too small a quantity to be effective.

For an antioxidant serum, look for the announced concentration: 10 or 15% for the ascorbic acid form. Without a number, nothing can be concluded about the product's effectiveness.

Active ingredients of the same family are recognized by their suffix: acids used in exfoliation all have the mention "acid" in the international list.

The role of the skin barrier

The outermost layer of the skin retains water and filters what enters. A weakened skin barrier allows active ingredients to pass through too quickly, which explains tingling sensations.

This is why an overly complex routine becomes counterproductive: it damages the mechanism on which hydration depends, and each product becomes less well tolerated than the previous one.

Ceramides or panthenol in the night cream help restore it. Two weeks are generally enough to restore skin capable of tolerating everything.

What skin type for which choice

Skin types influence the choice less than one might think: it is the objective that decides. The type mainly determines the frequency and the accompanying texture.

Oily skin will tolerate a sustained rhythm with a light gel; dry skin will require a spaced rhythm and a rich cream. The active ingredient, however, remains the same.

A useful clarification

These products are cosmetics and act on the appearance of the skin, without treating any condition. A spot that changes shape, color, or contour requires medical advice without delay.

Two ways to address a dull complexion

AHA removes dead cells on the surface, while vitamin C acts on the color itself: the first smooths skin texture, the second unifies. For skin with spots rather than roughness, an éclat serum concentrated with vitamin C is the most direct choice, with weekly exfoliation still recommended.