what causes blisters?
Most blisters happen from irritation or other damage to the skin from something outside the body, such as a shoe. Some illnesses can make blisters. A single blister is usually from friction or a burn, typically on the hands or feet.
1 Pemphigus vulgaris, a potentially fatal skin disease, causes blisters in the mouth or skin; these painful blisters become raw and crusted after bursting.  Bullous pemphigoid causes less severe blisters that heal faster and are not life-threatening; this condition is seen mostly in elderly people.