Why Skin Changes Vary on Feminising Therapy

Evidence Note

What is the question?

Feminising therapy acts on skin through two changes at the same time: it raises oestrogen and it lowers androgens. Those two changes do different jobs. Oiliness and acne follow the fall in androgens; collagen, thickness and hydration follow the rise in oestrogen. Because these two effects differ, and because how strongly each one lands depends on the individual, the result is a combination rather than a single fixed outcome. This note explains the main reasons that combination varies.

What does the evidence say?

The two processes are related, but do not always contribute equally. The best-supported change is less oily skin, and often improved acne — that follows androgen withdrawal and happens for most people. The oestrogen-driven changes (collagen, thickness, hydration, and what many people describe as a “glow”) are slower and far less certain. This probably explains why some people notice a marked drop in oiliness with relatively modest changes in skin texture, while others report proportionally greater changes in skin texture than in oiliness.

Free hormone may matter more than total. Skin cells are thought to respond most closely to the free (unbound) fraction of circulating hormone rather than the total concentration reported on routine blood tests, although this has not been demonstrated directly in transfeminine skin. SHBG, a carrier protein, is one of the main determinants of that free fraction. It offers a plausible reason two people with the same blood oestradiol can still differ: someone with high SHBG has less free testosterone (a stronger anti-oily effect) and also less free oestradiol (a weaker “glow” effect). It is a plausible mechanism rather than a measured fact, but it fits the pattern.

Route and dose feed into the same thing. Oral oestradiol usually raises SHBG more than transdermal preparations (patches or gel), which changes the balance between free and bound hormone; dose may also influence this balance. Whether this translates into measurable differences in skin outcomes has not been studied in trans women, but it is one plausible explanation for why outcomes may differ.

You start from different places. Baseline skin type, age, ancestry and skin tone (which sets melasma risk), how oily the skin was to begin with, and how much androgen exposure there had been all shape what changes and by how much.

Time changes the picture. Oiliness and acne usually shift within the first months; any collagen or thickness effects are slow and may take a year or more. Skin at six months is not the final answer.

How strong is the evidence?

The direction of each of these drivers is well understood; what is missing is the size of each one in trans skin specifically, which has barely been measured (the companion review grades this in detail). The free-hormone/SHBG explanation in particular is a well-grounded hypothesis, not a proven cause — it is offered as a likely contributor, not the whole story.

Where are the uncertainties?

No one has measured how much of the person-to-person variation each of these factors actually explains in transfeminine skin. There is almost no objective before-and-after skin data in trans women at all, so most of what can be said about why skin varies is reasoning from mechanism rather than from measurement.

Different skin on the same hormones is usually the biology behaving normally — not the treatment failing.

What does this mean for practice?

Expect variation, and be cautious about reading someone else’s skin outcome as a target for your own — the same regimen can land differently for reasons that have nothing to do with doing anything wrong. If a clinician is trying to understand why responses differ, free (or calculated free) oestradiol and testosterone together with SHBG may ultimately prove more informative than total concentrations alone — though this has not yet been shown for skin outcomes. For anyone prone to pigmentation, daily broad-spectrum and, ideally, tinted sunscreen is the single most useful step. And none of this is a reason to change how hormones are taken — that is a decision for you and your clinician, made for the whole body, not the skin alone.