Human hair (80 microns wide) and hyphae of Penicillium
When looking at tiny things it is sometimes hard to relate the size to things we are familiar with. In my intro mycology class I get students to mount a hair from their head on a slide, along with the hyphae of a common mould such as Penicillium to indicate the scale.
Some fungi specialize in keratin i.e. they are keratinolytic (lyse keratin) or keratinophilic (love keratin). Keratin is the stuff of hair, feathers, skin, hide, etc. and the fungi often don't wait until you shed so attack while the hair is on the beast so to say!
A common disease of humans caused by keratinolytic fungi is Athletes Foot. Also, the so-called 'Ringworm' diseases of the skin.