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RO Diffuse thinning describes what is seen, not what is happening. It means hair density falling evenly across the scalp instead of receding along a front. Several different processes produce that appearance, and they have different answers — so the word is the beginning of an assessment, never the end of one.
| Possibility | What points to it |
|---|---|
| Pattern loss, diffuse type | Gradual over years; back and sides spared |
| Telogen effluvium | Sudden shedding weeks after a trigger; hairs full thickness |
| Diffuse unpatterned alopecia | Thinning that includes the donor area itself |
| Systemic cause | Thyroid disease, iron deficiency, medication |
It shows up wet before it shows up dry. Dry hair sits apart and casts shadow; wet hair clumps and lets light reach the scalp. This is why people notice thinning in the shower or in overhead light months before it is visible in a mirror, and why photographs taken under different conditions are not comparable.
Whether the back of the head is involved is the decisive question. Thinning confined to the top, with a dense stable donor, is a candidate for surgery. Thinning that includes the occiput is not, whatever the top looks like, because the hair that would be moved is itself changing.
Related terms
For why thinning appears first on wet hair, see seeing your scalp when hair is wet. For scalp visible through dry hair, see seeing scalp through your hair.
