Acids 101:
The Glow Science
From ungluing dead skin cells to deep-pore vacuuming, chemical acids are the most effective way to refine texture—if you respect the barrier.
The Molecular Spectrum
AHA
Water-Soluble
Glycolic/Lactic. Dissolves surface "glue" to reveal fresh skin.
BHA
Oil-Soluble
Salicylic. Penetrates sebum to clear pores and blackheads.
PHA
Large Molecule
Gluconolactone. Extremely gentle exfoliation + hydration.
Azelaic
Dicarboxylic
Kills acne bacteria and inhibits melanin overproduction.
The Multi-Tasking Molecule
Unlike AHAs and BHAs which focus primarily on exfoliation, Azelaic Acid is a dicarboxylic acid that acts as a gentle leave-on treatment. It targets three major skin concerns simultaneously without the high irritation profile of other actives.
Bactericidal: Reduces P. acnes bacteria within the pores.
Tyrosinase Inhibitor: Prevents the formation of post-acne dark spots (PIH).
Anti-Inflammatory: The gold standard for reducing redness and Rosacea symptoms.
Clinical Usage (Az)
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Concentration
10% (OTC) to 15-20% (Prescription strength like Finacea).
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Texture Note
Can be "grainy" or silicone-heavy; apply before heavy creams.
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Compatibility
Safe to use with Tretinoin and Niacinamide.
The pH Threshold
An acid's strength isn't just about percentage. The Free Acid Value is dictated by the product's final pH.
If pH is too high, the acid is neutralized into a salt, losing its ability to exfoliate.
Formulation Matters
Don't play "Kitchen Chemist." Acid efficacy is a delicate balance of molecular size and acidity. Layering incorrectly can lead to chronic inflammation.
Avoid Vitamin C (L-AA)
Significant pH conflict causes compounded irritation.
The 20-Minute Rule
Wait for the skin pH to naturally reset before applying basic moisturizers.
Skip Physical Scrubs
Mechanical and chemical exfoliation together lead to micro-tears.
The "Safe Start" Protocol
Preventing the dreaded barrier-burn through methodical introduction.
The 2-2-2 Rule
Apply twice a week for two weeks. If no redness occurs, increase frequency to three times weekly.
Forearm Patching
Apply to the inner elbow for 48 hours. If it reacts here, skip the face.
The Sunscreen Link
AHAs increase photosensitivity by 50%. Using acids without daily SPF 30+ causes hyperpigmentation.
The Stinging Myth
Persistent burning is a signal to rinse immediately. Mild tingling for 30 seconds is normal.