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Skin concerns

Acne

Sebum, blocked pores and inflammation, tangled together.

Start here

What it is

Pores blocking up and becoming inflamed. Everything from small bumps to painful red lesions sits under one name.

Why it happens

Sebum rises, keratin at the pore opening thickens and plugs it, bacteria grow inside, and inflammation follows. These four do not run in order — they feed each other.

Where to start

This is a concern where cosmetics can do relatively little. If there is inflammation, or if marks are being left behind, start with the medicines layer.

There are no numbers and no citations in this box. What has been established, and how far, is below.

The first thing worth knowing about acne is the limit of what a cosmetic is allowed to do.

In Korea's functional-cosmetics rule (Annex 4), the only notified acne active is salicylic acid at 0.5%, and only in cleansing products. Leave-on products are not covered.

So this concern runs across three layers of this site: topical ingredients, medicines (adapalene, benzoyl peroxide, tretinoin, azelaic acid) and procedures. A cosmetic cannot claim to treat a disease, and we do not write as if it could.

Evidence level
Moderate evidenceAcid

Salicylic acid

Salicylic Acid

Most acne trials used 30% peels performed in a clinic. What Korea allows as an acne functional claim is 0.5%, and only in rinse-off cleansers. There is a sixtyfold gap between those two numbers.

Moderate evidenceOther

Tea tree oil

Melaleuca Alternifolia Leaf Oil

In a double-blind trial of 60 people using a 5% gel for 45 days, total lesion count and acne severity improved significantly more than with placebo — 3.55 and 5.75 times more, respectively. It is one trial, and 45 days is short.

Moderate evidenceAntioxidant

EGCG (green tea polyphenol)

Epigallocatechin Gallate

In a trial splitting 90 people into three arms over four weeks, sebum fell significantly in all three (P < .01). But all three received a moisturising cream with an active in it — there was no arm that got the base alone. For acne, there is one 8-week randomised split-face trial.

Moderate evidenceOther

Lactoferrin

Lactoferrin

There are two placebo-controlled randomised trials, and the endpoint is a lesion count. Mechanically, that passes this site's conditions for 'strong evidence'. But the large trial (168 people) put three things in one capsule — lactoferrin, vitamin E and zinc — and the trial that isolated lactoferrin (36 people) is the smallest. In that 36-person trial, inflammatory lesions fell 38.6% against placebo, total lesions 23.1%, and sebum 31.1%. The conditions count designs; they cannot count what was inside the capsule. So we lowered the badge by hand.

Early researchAcid

Mandelic acid

Mandelic Acid

A 50-person randomised trial compared a 45% mandelic acid peel against a 30% salicylic acid peel over 12 weeks. Overall acne score improvement did not differ, but salicylic acid did better on non-inflammatory lesions and mandelic acid on inflammatory ones. And adverse effects were fewer with mandelic acid. But nothing was left untreated.

Not establishedOther

Lactobacillus (probiotic and microbiome skincare)

An ingredient class — not a single line on an ingredient list

A 2026 systematic review and meta-analysis gathered five randomised trials, 332 participants. Non-inflammatory lesions (mean difference −1.39, 95% CI −5.10–2.32, P = .46), inflammatory lesions (−0.08, −1.28–1.11, P = .89) and total lesion counts (−9.07, −20.71–2.57, P = .13) — none of the three reached significance.

Not establishedOther

Oral zinc

Zinc Sulfate

This is swallowed. The randomised trials we found are two, and both are from 1977. In the placebo-controlled one, the placebo group also improved significantly and there was no significant difference between the groups. In the other, it tied with tetracycline — but there was no placebo arm, so whether both worked or neither did is something that design cannot separate.

Not establishedOther

Snail secretion filtrate

Snail Secretion Filtrate

We found one randomised placebo-controlled trial. 66 people over 12 weeks is a decent size, but it tested a serum of snail filtrate with calendula and liquorice root, not snail alone. One endpoint reached significance — inflammatory acne lesions — with a confidence interval running from −65.24 to −2.53. Non-inflammatory lesions, sebum, hydration, water loss, erythema and the users' own satisfaction all showed no difference.

Medicines used for this concern

Medicines are not listed alongside cosmetic ingredients. Dosage and whether a prescription is needed are settled in consultation.

Clinical procedures related to this concern

Procedures are not listed alongside topical ingredients. They are not something you use at home.