Glycolic Acid (AHA)
Retinaldehyde (Retinal)
How to Layer These Actives in Your Routine
Glycolic Acid (AHA)
Apply first to clean, dry skin. Operates at pH 3.2–3.8.
Avoid layering in the same evening session.
Retinaldehyde (Retinal)
Layer over the initial active. Operates at pH 5.5–6.5.
Biochemical Mechanism & Pharmacology
Applying Retinaldehyde (Retinal) concurrently with Glycolic Acid (AHA) multiplies stratum corneum lipid extraction and disrupts epidermal barrier integrity. Low-pH acids (< pH 3.8) can inhibit the esterase enzymes required for retinoid activation while causing severe trans-epidermal water loss and retinoid dermatitis.
Glycolic Acid (AHA) operates at low acidic pH (3.2–3.8), whereas Retinaldehyde (Retinal) functions best near physiological skin pH (5.5–6.5). Alternate them onto separate evenings to allow your lipid barrier to rest.
Recommended 7-Day Routine Blueprint
| Morning (AM) Routine | Evening (Night A) | Evening (Night B) |
|---|---|---|
✓Gentle Hydrating Cleanser ✓Hydrating Serum ✓Broad-Spectrum SPF 50+ | •Retinaldehyde (Retinal) (Retinoid Night) •Physiological Ceramide Cream | •Glycolic Acid (AHA) (Exfoliation Night) •Barrier Repair Cream |
Obstetric & Pregnancy Safety Summary
View Full Pregnancy Directory →Glycolic Acid (AHA) is classified as CAUTION LOW DOSE during pregnancy, while Retinaldehyde (Retinal) is classified as DEFER IN PREGNANCY under clinical guidelines. Always cross-reference with your physician if expecting.