Blood blisters form under the epidermis, the outermost layer of skin where new skin cells grow. [ 3 ] As skin new cells develop and your skin heals, the blood gradually dries out and the blister ...

An infected blister often contains white or yellowish pus (a mixture of dead tissue and immune cells), which may ooze from the blister if you apply pressure, says Dr. Brod.

Because sun blisters are second-degree sunburns, they affect both the top layer of skin (the epidermis) as well as the layer underneath that includes blood capillaries and nerve endings (the ...