Summary of "Skincare myths I used to believe"

Main takeaway

Be skeptical of claims that “sound right,” even when they come from peer‑reviewed papers or authority figures. Check proposed mechanisms, methods, and real‑world tests — and be aware of cognitive biases like authority bias and the illusory‑truth effect.

Myths debunked

Myth 1 — Chemical sunscreens need 20–30 minutes to “activate”

Why it’s wrong Chemical and mineral sunscreens both block UV immediately. Simple tests (for example, a UV torch applied to sunscreen on paper) show instant UV blocking.
Why packaging often says to wait Letting sunscreen dry down reduces rub‑off and helps makeup sit on top. Instructions that recommend waiting also discourage people from applying sunscreen only after they’ve already been sun‑exposed.
Practical tip Sunscreen begins working right away. Apply a sufficient amount, let it dry so it won’t rub off, and don’t delay application until after you’ve already been in the sun.

Myth 2 — The percentage on a product tells you how well it will work

Why it’s wrong Listed ingredient percentages do not equal delivered dose. Stability, formulation, packaging, delivery systems, and skin penetration determine how much active actually reaches target layers.
Things that matter more than percentage
- Ingredient stability (for example, retinol is prone to breakdown)
- Packaging (airtight tubes can be better than some “airless” pumps)
- Stabilizers, encapsulation, solvents, and penetration enhancers
- Clinical testing and meaningful efficacy data (not just marketing statements)
Practical tip Prefer products with good formulation, demonstrated stability, and clinical efficacy data instead of judging solely by percentage labels.

Myth 3 — Peeling gels “peel off skin”

Why it’s wrong The visible “rolls” are mostly product plus oil picked up from the skin, not large amounts of living skin. Simple demonstrations (glove tests, adding oil) show the effect stems from oil–product interaction.
Why it’s OK Peeling gels function as very gentle physical exfoliants — useful for managing clogged pores, tretinoin‑related peeling, and small flaky areas (e.g., around the nose). They are generally less harsh than scrubs or picking.
Practical tip Use peeling gels for gentle exfoliation prior to makeup; don’t fear them as removing living skin.

Myth 4 — Hyaluronic acid (HA) holds 1,000× or 6 L water per gram (and dries skin unless occluded)

Why it’s wrong The dramatic “thousand times” or “6 L per gram” claims lack solid evidence and appear to be exaggerations traced through weak citations. Experimental data suggest HA binds roughly 0.4–0.85 g water per g HA (40–85% of its weight), much lower than those sensational numbers.
On the idea that HA “sucks” water from skin if used alone This is mechanistically implausible — humectants form short‑range hydrogen bonds and cannot pull water long distances out of the skin. Most serums/creams already contain plenty of water for humectants to act on.
Practical tip HA is useful but not magical. For dry skin or dry climates, use a humectant plus an occlusive/emollient (a complete moisturizer routine). Applying HA to damp skin can make spreading easier but doesn’t fundamentally change efficacy; some brand trials (e.g., The Ordinary) showed similar effects on dry vs damp skin.

Other practical recommendations & science‑y notes

Look for clinical testing and robust formulation details rather than relying only on ingredient percentages.
Stabilizers and packaging matter (antioxidants, encapsulation, good tubes); not all “airless” pumps are truly airtight.
Different polymers have different water‑binding capacities: for example, some polyacrylates can bind far more water by weight than HA — but higher binding capacity doesn’t automatically mean “better” humectant performance in skin.
Safely testing simple demonstrations yourself can reveal marketing theatrics (e.g., UV torch, glove tests).
Maintain a balanced moisturizing approach: combine humectants + emollients + occlusives for effective hydration.

Notable people, products, organizations and references mentioned

Speaker: Michelle — chemistry PhD and skincare communicator
Other communicators: Stephen Ko (Kind of Stephen, Poems from the Lab)
Brands/websites: Paula’s Choice / Paula, Skinacea, The Ordinary (2% Hyaluronic Acid + B5 serum)
Organizations / sources: Cosmetic Ingredient Review (CIR), peer‑reviewed journals (including an Australian doctors’ journal referenced)
Ingredients/products discussed: chemical vs mineral sunscreen, hyaluronic acid, glycerin, polyacrylates, retinol, peeling gels, tretinoin
Demonstrations/tests referenced: UV torch + paper test, glove tests on peeling gels, The Ordinary clinical test of HA on dry vs damp skin