AHA: myth or real effect on the skin

The myth: the higher the percentage, the better. Two serums with the same number can act very differently, and the deciding number is almost never printed.

What AHAs are

Alpha-hydroxy acids, a family of water-soluble acids often called fruit acids — which is partly misleading, as most are now produced synthetically or by fermentation. Glycolic acid historically comes from sugarcane extract, lactic acid from milk, citric acid from citrus fruits, malic acid from apples.

Their action consists of breaking down the bonds that hold dead cells together on the surface. These cells then detach on their own, which refines skin texture and revives the complexion's radiance.

pH, the missing number

An acid only acts in its free form, and the free part depends on the formula's pH. At pH 3.5, most of the acid is active; at pH 5, most of it is neutralized and the product exfoliates little, regardless of the stated percentage.

A 5% serum at pH 3.2 can therefore be more active than a 10% cream at pH 4.5. The percentage measures the quantity present, not the quantity that works. Most brands do not display the pH, and this is the most useful missing information.

Molecule size, the other variable

Glycolic acid is the smallest in the family: it penetrates quickly and acts strongly. Lactic acid is larger, therefore slower and better tolerated – it is also one of the skin's natural moisturizing factors, making it the only AHA to hydrate while it exfoliates.

For dry and sensitive skin, the latter is the first choice. For normal to oily skin seeking faster results, glycolic acid is more suitable. This is not a scale of quality but a scale of intensity.

What AHAs actually do

Smoother skin texture in three to four weeks, brighter complexion in six to eight. Partial reduction of old marks over three months. These are well-documented and measurable effects, provided you maintain consistency.

For established wrinkles, there is nothing to expect. For pores, the improvement concerns their visibility — their content — not their diameter, which cannot be reduced by cosmetic means.

Rhythm, more important than dose

Two applications per week to start, three at most thereafter. Beyond that, improvement reverses: the skin becomes reactive and the benefit is lost. This is the point where most users fail, long before the question of concentration.

Sun protection is mandatory with any exfoliation: the new layer of skin is younger and marks more easily. This is not a comfort precaution, but a condition of use.

So, myth or real effect

Real and well-established effect, myth about the percentage. The best product is not the most concentrated: it's the one whose pH is adapted to your skin and that you will still be using in six months.

Our lactic acid AHA peel combines the acid with a humectant, which limits the drying effect, and the rosewater brightening toner offers a lower concentration for frequent use.

How to integrate AHAs into a routine

In the evening, on clean and dry skin, before moisturizing. Twice a week to start, increasing by one application every three weeks if the skin tolerates it. On acid-free evenings, a regular routine.

It is recommended never to combine them with a retinoid on the same evening, nor with a mechanical scrub, nor with a second acid. These rules prevent almost all irritations, and they are more important than the choice of product.

For sensitive skin

AHAs are still possible, provided you choose lactic acid and a low concentration — 5% or less — with a very gradual increase. One application every ten days for a month, then every seven.

If the skin peels, reddens, or becomes reactive, you should space out applications rather than stop. The frequency is almost always to blame before the formula, and resuming more slowly usually resolves most situations.

What becomes visible, and when

More even skin texture from the third or fourth week. A brighter complexion after six to eight weeks. Partial reduction of old marks over three months. For imperfections, the effect is indirect: eliminating dead surface cells limits what clogs pores, without acting within the pore as salicylic acid would.

In terms of anti-aging, the contribution focuses on the surface: smoother skin better reflects light, which reduces the appearance of fine lines. No concentration acts on established wrinkles.

What to avoid

Using an AHA in the morning without sun protection. Applying two exfoliating treatments in the same week. Increasing the concentration because the product "is no longer working" when it is simply that the surface renewal has reached its normal pace.

A well-used acid becomes unnoticeable. This is a sign that it is working, not that it has stopped acting.