A flat blood blister under the skin is when a blood vessel ruptures and collects in tissues under the skin. The cause of a blood blister can be due to some injury that either pinches or squeezes the skin, states Foot Vitals. In most instances, these blisters tend to develop on toes or fingers.
These blister types can form as the result of handling tools or objects that can pinch the fingers. The formations of toe or feet blisters also are common in athletes who participate in sports, such as running. Unless they become infected, blisters will resolve on their own with some simple at-home treatments.
To treat a blood blister, it is important to refrain from doing the activity that caused the injury, bandage it and then leave it alone, suggests WebMD. Another treatment that may be useful to diminish pain is to place a cold compress over the affected area and then bandage it, states Utah Mountain Biking. It is also advisable to keep the area clean and bandaged until it heals, which can take up to 2 weeks.
Someone with a blood blister can also check for signs of an infection, which can include inflammation, pain, tenderness or pus discharge. If these symptoms or numbness are present, then he should see a doctor.