(HealthDay News) -- A blister, medically called a vesicle, is a small sac on the skin that's filled with fluid. Blisters can be caused by friction or an underlying health issue.

The U.S. National Library of Medicine says the following illnesses and conditions can lead to blisters:

• Having an allergic reaction to a medication.
• Having eczema (atopic dermatitis).
• Having a skin disease, such as dermatitis herpetiformis or porphyria.
• Having chicken pox or shingles.
• Having contact dermatitis, such as from poison ivy.
• Having the herpes simplex virus.
• Having the skin infection impetigo.