Chemical exfoliation guide
What's the difference between AHAs, BHAs, and PHAs and which do I need?
Projekt-Plan
Why: Different acids target specific skin layers and issues; choosing the wrong one can lead to irritation or zero results.
How:
- Check for oily skin or clogged pores (indicates a need for BHA).
- Check for dryness, sun damage, or fine lines (indicates a need for AHA).
- Check for extreme sensitivity or rosacea (indicates a need for PHA).
Done when: You have clearly defined whether you need surface exfoliation, pore-clearing, or ultra-gentle care.
Why: Understanding the chemistry prevents you from over-exfoliating or using incompatible ingredients.
How:
- AHAs (Alpha Hydroxy Acids): Water-soluble, works on the surface. Best for brightening and anti-aging (e.g., Glycolic or Lactic acid).
- BHAs (Beta Hydroxy Acids): Oil-soluble, penetrates pores. Best for acne and blackheads (e.g., Salicylic acid).
- PHAs (Polyhydroxy Acids): Large molecules, very gentle and hydrating. Best for sensitive skin (e.g., Gluconolactone).
Done when: You can explain the basic difference between the three acid types.
Why: Certain medications and conditions make chemical exfoliation dangerous for the skin barrier.
How:
- Ensure you have not used Isotretinoin (Accutane) in the last 6 months.
- Confirm you do not have active infections, cold sores, or open wounds on the treatment area.
- If pregnant, consult a doctor before using BHAs (Salicylic acid), as high concentrations are often restricted.
Done when: You have confirmed your skin is healthy enough for chemical actives.
Why: Starting with high percentages (e.g., 30% peels) as a beginner can cause chemical burns.
How:
- For AHA: Look for a 5-10% Lactic Acid or 5% Glycolic Acid toner/serum.
- For BHA: Look for a 1-2% Salicylic Acid liquid or gel.
- For PHA: Look for a PHA-based toner (often labeled as 'Gluconolactone').
- Choose a fragrance-free formula to minimize irritation.
Done when: You have a beginner-friendly exfoliating product ready for use.
Why: Chemical exfoliants increase photosensitivity, making your skin significantly more prone to sun damage and burns.
How:
- Select a broad-spectrum sunscreen (protects against UVA and UVB).
- Ensure it has at least SPF 30.
- Choose a formula that you enjoy wearing daily, as this is a non-negotiable step.
Done when: You have a reliable sunscreen to protect your newly exfoliated skin.
Why: To prevent a full-face allergic reaction or severe irritation.
How:
- Apply a small amount of the product to a discreet area (e.g., behind the ear or inner forearm).
- Wait 24 hours to monitor for redness, itching, or blistering.
- If no reaction occurs, proceed to facial application.
Done when: You have confirmed the product is safe for your specific skin chemistry.
Why: Applying acids to damp skin increases penetration, which significantly raises the risk of irritation for beginners.
How:
- Use a gentle, pH-balanced cleanser.
- Pat your face dry with a clean towel.
- Wait 2-3 minutes to ensure the skin is completely bone-dry before applying the acid.
Done when: Your skin is clean, dry, and ready for the active ingredient.
Why: Exfoliation is best done at night to allow the skin to recover without immediate UV exposure.
How:
- Apply a thin layer of the product, avoiding the eye area, lips, and nostrils.
- If using a liquid, use a cotton pad or pat it on with clean hands.
- Do not rinse off unless the product instructions explicitly state it is a 'mask' or 'peel'.
Done when: The product is applied correctly to the target areas.
Why: Acids can temporarily disrupt the skin barrier; a moisturizer prevents trans-epidermal water loss.
How:
- Wait about 1-2 minutes for the exfoliant to settle.
- Apply a moisturizer containing ceramides, glycerin, or hyaluronic acid.
- Avoid using other 'actives' (like Retinol or Vitamin C) in the same session during the first few weeks.
Done when: Your skin is hydrated and the barrier is supported.
Why: Exfoliation thins the top layer of dead skin, leaving fresh cells vulnerable to UV damage.
How:
- Use the two-finger rule (apply two strips of sunscreen to your index and middle fingers) for full face and neck coverage.
- Reapply every 2 hours if spending time outdoors.
Done when: Your skin is protected from post-exfoliation sun sensitivity.
Why: Over-exfoliation can lead to a 'shiny' but damaged barrier, causing breakouts and sensitivity.
How:
- Use the product only once a week for the first 14 days.
- Observe for signs of over-exfoliation: stinging when applying moisturizer, unusual redness, or a tight 'plastic' look.
Done when: You have completed two weeks of controlled, low-frequency use.
Why: Skin tolerance builds over time; increasing frequency too fast is the most common mistake.
How:
- If your skin feels healthy after 2 weeks, increase to twice a week (e.g., Monday and Thursday).
- Most people find their 'sweet spot' at 2-3 times per week. Daily exfoliation is rarely necessary for AHAs/BHAs.
Done when: You have established a sustainable routine that doesn't cause irritation.
Why: BHAs especially can cause a temporary increase in breakouts as they clear out deep-seated clogs.
How:
- Distinguish between purging (breakouts in areas where you usually get them) and irritation (breakouts in new areas or itchy rashes).
- If purging occurs, stay consistent; it usually resolves within 4-6 weeks.
- If irritation occurs, stop use immediately and focus on hydration.
Done when: You can identify whether your skin is adjusting or reacting negatively.