From about 2020 I wore a topper nearly every day I left the house, and it gave me my head back. What nobody warned me about was what was happening underneath it.
Can you wear a hair topper with seborrheic dermatitis?
Yes, but it's worth planning around. A topper is lovely on top and a bit of a greenhouse underneath. Warm, covered, no air moving. If your scalp already leans towards seb derm, that's a nice little hotel for the yeast that drives it.
Plan topper days around wash days
If I know I'm wearing a piece, I wash that morning and get my own hair bone dry first, because damp hair under a base is asking for trouble. And nothing heavy goes on my scalp. No oils, no thick leave-in serums. The stuff that feels soothing at 11pm on a bare scalp turns into a sealed layer the second you clip something over it.
Rotate your shampoos
This is the single thing that helped me most. Most medicated shampoos lean on one active: ketoconazole, piroctone olamine, zinc pyrithione or selenium sulphide. Salicylic acid is the odd one out, because it lifts the scale so the others can reach your skin. The research on why one shampoo stops working is thinner than people suggest, but rotating stopped my "this used to work and now it doesn't" cycle.
Wash the topper too
It's quietly collecting your sweat, oil and dead skin, and mid-flare that includes yeast. So I wash the base with a sulphate-free shampoo and let it air dry on a stand, never scrunched in a towel (Pureology Strength Cure has done my pieces for years).
The rest, including the clip side and the days I just don't wear it, is in my hair topper and seborrheic dermatitis post.