Glycolic Acid (AHA) Peeling: Complete Guide

Glycolic acid is the gold standard of alpha-hydroxy acids (AHAs). It has the smallest molecular size of all AHAs, allowing it to penetrate skin deeply — dissolving dead cells, smoothing texture, and revealing brighter skin. Here's how to use it correctly.

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What Is Glycolic Acid?

Glycolic acid is an alpha-hydroxy acid (AHA) derived from sugarcane. Its molecular weight is just 76 Daltons — the smallest of all AHAs — which means it penetrates skin easily and effectively.

How It Works:

1. Dissolves desmosomes — the "glue" that holds dead skin cells together
2. Accelerates cell shedding — reveals fresh, smooth skin underneath
3. Stimulates collagen — long-term use increases dermal thickness
4. Improves hydration — increases hyaluronic acid and NMF in skin
5. Reduces hyperpigmentation — disperses melanin clusters

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AHA Family Comparison

| AHA | Source | Molecular Weight | Penetration | Gentle? | |-----|--------|-----------------|-------------|---------| | Glycolic Acid | Sugarcane | 76 Da | Deepest | Moderate | | Lactic Acid | Milk/fermentation | 131 Da | Moderate | Gentle | | Mandelic Acid | Bitter almonds | 152 Da | Surface | Very gentle | | Tartaric Acid | Grapes | 150 Da | Surface | Gentle | | Citric Acid | Citrus | 192 Da | Surface | Gentle |

Key takeaway: Glycolic is the most effective AHA but also the most potentially irritating. If you have sensitive skin, start with lactic or mandelic acid instead.

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Benefits of Glycolic Acid

Proven Effects:

• Smoother texture — removes dead skin buildup
• Brighter complexion — reveals fresh skin cells
• Reduced hyperpigmentation — fades dark spots and post-acne marks
• Minimised pore appearance — clears pore openings
• Enhanced product absorption — removes the barrier of dead cells
• Increased collagen — long-term use improves skin firmness
• Reduced fine lines — mild wrinkle improvement over months

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Concentration and pH: What Matters

Concentration:

| Concentration | Use | Results | |---------------|-----|---------| | 4–7% | Daily toner/exfoliant | Gentle maintenance | | 7–10% | 2–3× per week serum | Visible improvement | | 10–15% | Weekly treatment | Strong exfoliation | | 15–30% | Professional peel | Best done by a professional |

pH:

Glycolic acid is only effective at pH below 4.0. At higher pH, it's neutralised and ineffective. Well-formulated products have pH 3.0–3.8.

To check pH: Use pH test strips on your product. If it's above 4, it's not working.

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Best Glycolic Acid Products in the UK

The Ordinary Glycolic Acid 7% Toning Solution — ~£7

7% glycolic acid + amino acids + ginseng + aloe. pH 3.5–3.7. Excellent entry-level product. Buy: Amazon UK

Paula's Choice 8% AHA Gel Exfoliant — ~£30

8% glycolic acid + green tea + salicylic acid (for pore penetration). Gel texture, soothing formula. Buy: Amazon UK

Pixi Glow Tonic — ~£16

5% glycolic acid + aloe + ginseng. Gentle, great for beginners. Available at Boots. Buy: Amazon UK

Medik8 Sleep Glycolic — ~£30

10% glycolic acid overnight treatment with buffering ingredients. Time-released for gentle exfoliation. Buy: Amazon UK

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How to Use Glycolic Acid

In Your Routine:

1. Cleanse and pat dry
2. Apply glycolic acid (toner: with cotton pad; serum: with fingers)
3. Wait 2–3 minutes for pH to work
4. Apply hydrating serum (HA, niacinamide)
5. Apply moisturiser to seal

Frequency:

| Skin Type | Frequency | |-----------|-----------| | Sensitive | 1× per week | | Normal | 2–3× per week | | Oily/Resistant | 3–4× per week |

Never use glycolic acid on the same night as retinol. Alternate nights.

Important Rules:

• Always wear sunscreen the next day — AHAs increase sun sensitivity by 50%
• Don't use physical scrubs on the same day
• Avoid other acids (BHA, Vitamin C) on the same night
• Start with lower concentrations and build up

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Side Effects and Who Should Avoid

Common Side Effects:

• Mild stinging upon application (normal for first few uses)
• Temporary redness
• Slight flaking for 2–3 days after first use

Do NOT Use Glycolic Acid If:

• You have active eczema or rosacea on the application area
• Your skin barrier is damaged (stinging from basic products)
• You're using prescription retinoids (tretinoin, isotretinoin) — consult your doctor
• You have very sensitive skin (use mandelic acid instead)

During Pregnancy:

Glycolic acid at low concentrations (≤10%) is generally considered safe during pregnancy. Avoid professional-strength peels.

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FAQ — Glycolic Acid

Can I use glycolic acid every day?

Only low-concentration toners (4–5%) are suitable for daily use. 7%+ concentrations should be used 2–3 times per week maximum. Over-exfoliation damages the skin barrier.

Does glycolic acid help with acne scars?

Yes, for superficial acne marks (post-inflammatory hyperpigmentation). Glycolic acid accelerates cell turnover, fading dark marks faster. For deep pitted scars (ice pick, boxcar), you need professional treatments like microneedling or laser.

Can I use glycolic acid and retinol together?

Not on the same night. They both increase cell turnover and can severely irritate skin when combined. Use glycolic acid 2–3 nights per week, retinol on the other nights.

Is glycolic acid better than salicylic acid?

They do different things. Glycolic (AHA) is water-soluble and exfoliates the surface — best for texture, tone, and brightness. Salicylic (BHA) is oil-soluble and penetrates pores — best for acne, blackheads, and oiliness. Many people benefit from both on different nights.

How long until I see results from glycolic acid?

Immediate skin smoothness after 1–2 uses. Visible brightening and tone improvement after 2–4 weeks. Significant results (hyperpigmentation reduction, fine line improvement) after 2–3 months of consistent use.