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Rash behind ear, Darier's disease is a hereditary disease like that.
It appears as skin color papule on upper trunk, neck, behind ear and groin. skin rash
aggravates during summer. they itch sometimes and fine scale may developed at the top on lesion. when you remove this scale there will remain a pit like depression
. A foul odor may develop from rashes. All that things may give you a unwashed look.
But this type of rash is non-communicable so when it goes to your friend that might not darier's disease.
may be other possibility, if that you need to shampoo your head and neck with nizoral/ nizoder shampoo regularly for 10-15 minutes before bath.