1/8 inch of movement is natural, but you can feel like much more. When the shoes break in slowly, loose slipping in the heels will not cause any swellings or blisters. But if you wear shoes that are too small in size and very much tight-fitted, then the shoes will rub the foot’s skin often and cause blisters. Before purchasing the shoes, wear the shoes and walk around in them to ensure a perfect fitting. Shoes should not be too tight or too loose; rather, it should be snugly fit.