Topical vitamin C
Strong laboratory rationale, a thin and short human trial base, and a formulation problem that most of the marketing quietly ignores.
Retinoids
The one topical category where the human trial base is deep enough to justify the confidence. Also the one most people abandon before it works.
Niacinamide
The most tolerable active in common use, with a plausible mechanism and a human trial base that is broader than it is deep.
Collagen supplements
One of the fastest growing supplement categories in the UK, resting on a trial base whose funding pattern should give any reader pause.
Vitamin D and immunity
The clearest example on this site of a claim that is well supported for one group of people and unsupported for everybody else.
Zinc and skin healing
A nutrient whose necessity is beyond dispute and whose supplement marketing rests on a claim the evidence does not make.
Polyphenols and photoprotection
The most scientifically interesting weak evidence base on this site. Excellent laboratory work, very little of it demonstrated in people.
Probiotics and the skin gut axis
A genuine and fast moving research field, and a marketplace selling conclusions the research has not yet reached.
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Nothing here is medical advice. Speak to a pharmacist, a GP or a dermatologist about your own circumstances.
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