Science & treatments
Most skincare advice assumes you know your skin type, and most people are guessing. These articles explain the Fitzpatrick scale, why faces get oily, the difference between dry and dehydrated skin, what the skin barrier is, and how far products can actually reach through its layers. Understanding these basics makes every other recommendation on the blog easier to apply.
Sensitive skin is a defined condition: stinging, burning or tightness from things that should not cause it. Some of it is early rosacea, eczema or an allergy, so start with simple checks.
Skin tone is colour, undertone is a makeup term for red or yellow, and skin type is oil and sensitivity. The Fitzpatrick scale is a fourth thing: sun reaction.
Oil output is set by hormones, age, sex and season, and the studies found no sign that washing raises it. What measurably lowers sebum is medicine, not a cleanser.
The barrier layer is 10 to 30 micrometres thick and the dermis beneath it up to 4 millimetres. Here is what reaches each layer, and what the paper behind the 28-day renewal claim actually reports.
Dry and dehydrated are two different deficits sharing one word, and the fix for one can worsen the other. In a head-to-head trial, moisturiser raised skin hydration and extra water did not.
The barrier has measurable correlates — water loss, pH, a lipid ratio — and almost nobody using the word refers to any of them. Including, until now, this site.
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