Topical Actives: Retinoid, Peptide, AHA/BHA Biochemistry

Retinoids: the gold standard

Retinoid is the general name for vitamin A derivatives. From weakest to strongest: retinyl palmitate < retinol < retinaldehyde (retinal) < adapalene < tretinoin (retinoic acid) < tazarotene. Tretinoin and tazarotene are prescription-only; tretinoin is easily accessible in Turkey, tazarotene is difficult. Retinol and retinal are over-the-counter.

Retinoids bind to receptors in the cell nucleus and alter the expression of approximately 500 genes. They increase collagen synthesis, disperse melanosomes (lighten spots), promote a more regular renewal process for keratinocytes, and reduce sebum production. Effects begin in 3-4 weeks and become noticeable in 3-6 months.

Peptides: signaling molecules

Peptides are short chains of amino acids; they bind to specific receptors in the skin and give specific commands. Prominent ones: Matrixyl (palmitoyl pentapeptide-4) triggers collagen synthesis; Argireline (acetyl hexapeptide-8) gently reduces muscle contraction at the surface level — the term "topical botox" is exaggerated but there is a small effect; Copper peptides (GHK-Cu) support wound healing.

The main problem with peptides is their molecular size; it is difficult for them to pass through the stratum corneum. In good formulations, penetration enhancers (liposomal delivery, structured molecules) are used.

AHA/BHA/PHA — acid classes

AHAs (alpha-hydroxy acids): glycolic, lactic, mandelic, almond acid. They work on the surface, loosen keratinocytes, and provide surface smoothness. They are effective for spots and fine lines. Concentration: 5-15% for home use; 30%+ for clinical peeling.

BHA (beta-hydroxy acid, salicylic): oil-soluble, penetrates into pores. It is primary for acne, blackheads, and sebum problems. 2% daily, 20-30% professional peeling.

PHAs (polyhydroxy acids, such as gluconolactone): larger molecules, milder effect, suitable for sensitive skin.