Hair
Not a stain and not really a soil — a keratin fibre that tangles, holds everything else, and defeats every wet method by floating.
In detail
Hair is a keratin filament, chemically stable and almost completely unaffected by cleaning products. That is the whole difficulty: nothing dissolves it at any strength a household would use, so every answer is mechanical. It behaves like no other household soil. It tangles with itself and with fibres, so a wet cloth pushes it into a rope rather than lifting it. It floats, so a rinse redistributes it. And it acts as a scaffold — hair caught in a brush, a plughole or a vacuum holds sebum, dust, product and lint that would otherwise have washed away, which is why the accumulation is always a mixture and never just hair. So the sequence is dry-first and mechanical: rake it out of a brush before any water, lift it out of a drain rather than flushing it, and vacuum a textile from several directions before anything wet. Professional carpet guidance adds that hair and dander left inside a vacuum decompose and make the exhaust the new source of the smell. One warning worth keeping. A drain blockage that is mostly hair is not a chemistry problem, and reaching for a drain product on it puts a caustic or oxidising agent into a pipe where nothing is going to dissolve.
Hacks and claims involving this
- Soaking a hairbrush to clean it Does not work
Sources for this page
Sources
Consumer Floor and Furnishings Care Information: carpet topics
Institute of Inspection, Cleaning and Restoration Certification (IICRC) · Trade or professional body
Relied on for: That dry vacuuming from several directions is the standing first step on textile furnishings, and that pet hair and dander left in a vacuum decompose and cause strong odours from the exhaust. (states this directly)
G.B. Kent & Sons plc (Kent Brushes) · Manufacturer documentation
Relied on for: That loose hair is combed out of a hairbrush with a dedicated raking cleaner before any washing takes place. (states this directly)