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What Are Blisters?

Whether from playing too much basketball or jogging in ill-fitting sneakers, we've all had blisters. But what are blisters, and how do they form?

orange and pink running shoes

Photo: sean dreilinger (Flickr)

Make sure to protect your feet to avoid getting blisters.

Remember that hit song from the 80’s that featured the chorus: “And I would walk five hundred miles / and I would walk five hundred more / Just to be the man who walks a thousand miles / to fall down at your door”? What sounds romantic in pop song fantasy would be painful in reality.

Walk Not So More

Anyone who walks a thousand miles would indeed fall down, thanks to the large blisters that would most likely form on the heels and soles of weary feet.

Whether from playing too much basketball or jogging in ill-fitting sneakers, we’ve all had blisters. But what are blisters, and how do they form?

All About Blisters

Blisters come in all shapes and sizes, and some are more serious than others. The typical, jogging-related blister is a round patch of elevated skin containing a clear fluid. Blistering occurs when an upper layer of skin rubs against the underlying layer.

As a space opens between the skin layers, chemicals cause the blood vessels in the area to leak and allow a clear fluid to seep out and fill the space between layers of skin. This fluid is a sort of clear plasma, or blood without the red blood cells.

Blisters usually occur in the uppermost layers of skin, and are normally harmless. Because the blood vessels are only made more porous but not actually damaged, red blood cells do not fill the blister. But if a blister does fill with red blood, it means the damage is more serious, and should be carefully treated.

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