My daughter woke up with this huge spot on her foot I don’t know what it could be. She’s been in pain and can’t move her foot what is this.. Explain this 😩

A blood blister can look alarming at first glance—a dark red or purple bubble under the skin that appears suddenly and often without warning. While they’re usually harmless, blood blisters can be uncomfortable and, in some cases, signal that something more is going on. Understanding what blood blisters are and how to handle them can help you treat them safely and know when to seek medical advice.

What Is a Blood Blister?

A blood blister forms when small blood vessels (capillaries) beneath the skin rupture but the skin itself remains intact. Blood becomes trapped under the surface, creating a raised, fluid-filled pocket that appears red, maroon, or purple—darker than a typical clear blister.

Blood blisters most commonly appear on:

• Fingers and palms

• Toes and soles of the feet

• Inside the mouth (cheeks, tongue, or gums)

Common Causes of Blood Blisters

Most blood blisters are caused by sudden pinching or repeated friction, such as:

• Slamming a finger in a door

• Wearing tight or poorly fitting shoes

• Using tools or sports equipment without protection

• Repetitive motions that create pressure on the skin

Blood blisters in the mouth can result from: