Its caused by intermitent compresion. The reason you are getting it can be pathological or physlogical its called hyperkeratosis, skin cells reproduce faster than descremation. most likely cause is your biomechanics, the way you walk, this could be that you are overpronating or you have a congenital condition from birth. My advise is see a podiatrist, not a foot health practioner who will just move the hyperkerotosis and then it comes back and this goes on costing you money, you might need an othotic making to corect this problem. Sometimes callus should not be removed as it is providing protection. Sorry but I dont see how reflexology is going to help, if it does let me know how.