Answer: Blister
Step-by-step explanation:
A blister is a fluid filled bubble like structure which develops in the uppermost layer of the skin that is epidermis. It may also form within the epidermis and dermis.
It develops due to friction, infection, freezing, burning, burns and contact with chemicals. Blister can also be caused due to diseases.
It can be filled with blood, plasma, serum and pus.