Snail mucin: the clearest case on this site of famous and well-evidenced not being the same thing

A 2022 trial at Chulalongkorn University in Thailand.

66 people with mild-to-moderate acne brought on by prolonged mask wearing — 'maskne' — took part. Randomised, double-blind, placebo-controlled, applied twice daily for 12 weeks.

What they used was a serum containing snail secretion filtrate, Calendula officinalis and Glycyrrhiza glabra root extract.

Results:

• In the mask-covered area, the percentage reduction in inflammatory acne lesions was greater than on placebo, at every time point.
• In numbers: −33.89% (95% CI −65.24 to −2.53, p = 0.03).
• A subgroup of 12 who were also using other acne treatments ran the same way.

Now how to read it.

First, snail mucin was not measured on its own. A three-ingredient serum was compared against placebo. So what this shows is not 'snail mucin reduces acne' but 'this three-ingredient serum beat the vehicle'.

One of the other two, liquorice root extract, has a literature of its own on inflammation. Whether the work was done by the snail, by the liquorice, or by all three together cannot be separated in this design. We said the same on the ectoine and astaxanthin pages.

Second, look at the confidence interval. −65.24 to −2.53. It could be 65% better than placebo, or 2.5% better. This trial does not say how large the effect is. It says probably not zero, and stops.

Third, this is maskne. Acne arising under prolonged mask wear is a particular condition, and nothing in this trial establishes that ordinary acne behaves the same way.

So it sits at 'not established'. The design was sound; the thing measured was not this ingredient.

Same trial, same 66 people. One endpoint reached significance above. Here is everything else they measured.

• non-inflammatory lesions (comedones) — no difference
• sebum levels — no difference
• stratum corneum hydration (corneometry) — no difference
• transepidermal water loss (TEWL) — no difference
• erythema score — no difference
• the participants' own satisfaction (10-point scale) — no difference

Why we give this list its own entry, at the same size.

What leads the pitch for this ingredient is not acne. It is moisture and soothing. And this trial measured exactly those — hydration, water loss, erythema.

None of them differed.

The paper's concluding sentence speaks of 'a role as an adjunctive treatment in maskne'. Quote that sentence alone and this list disappears. We do not let it disappear.

There are 66 people. Small differences could have been missed. But the inflammatory lesion result above was caught in those same 66. That one thing registered at this size and the rest did not is itself worth reading.

Note too that satisfaction did not differ. On GHK-Cu and PRP, self-assessment was the only thing that reached significance. Here it ran the other way: the one counted endpoint reached it and self-assessment did not.