tiger's itch

When the sweat runs down your back, into the crack of your arse. Then the chafing starts, followed by the redness.. then the itch... The "there's no socially acceptable, nor non-finger-smelling way to scratch" kind of itch.

I've been working my bollox off all day and worked up a fierce sweat. It's run right down my back and given me the worst case of Tiger's Itch I've ever had!