What Is The Treatment For Brown Blisters On The Foot?

hi, i have noticed on & off for months or possibly years, that i regularly on & off get brownish raised spots on the arch of my foot. It sometimes get itchy & if i scratch it it raised then if it 'pops' it is alot like a blister inside. My 5 year old son has the same thing at the moment. I also occasionally get the same spots on the outside of my big toe.