A blood blister can feel alarming when you first notice it. It often appears as a deep red or purplish bubble beneath the skin, sometimes developing quickly and without clear warning. While the sudden change in appearance can be concerning, most blood blisters are harmless and heal on their own.
They can still be uncomfortable, tender to the touch, and inconvenient depending on where they form. In some cases, however, frequent or unusual blisters may signal an underlying issue. Understanding what a blood blister is and how to care for it can help you respond calmly and know when medical advice may be helpful.
What Is a Blood Blister?
A blood blister forms when tiny blood vessels, called capillaries, break beneath the surface of the skin. The outer layer of skin remains intact, trapping blood underneath. This creates a raised, fluid-filled area that looks dark red, maroon, or purple.
Blood blisters often appear darker than typical blisters filled with clear fluid. Their size can vary from small and barely noticeable to larger and more uncomfortable.
They most commonly develop in areas exposed to pressure or friction, such as the fingers, palms, toes, and soles of the feet. They can also appear inside the mouth, including on the cheeks, tongue, or gums.
Common Causes of Blood Blisters
Most blood blisters occur due to sudden pinching or repeated friction that damages small blood vessels while leaving the skin unbroken.
Common causes include slamming a finger in a door, wearing tight or poorly fitting shoes, using tools or sports equipment without protective gloves, and repeated movements that place continuous pressure on the same area of skin.
Athletes, manual workers, and people who spend long hours on their feet may be more prone to developing blood blisters because of ongoing friction and pressure.
Inside the mouth, blood blisters can form after accidentally biting the cheek or tongue, undergoing dental procedures that irritate soft tissue, wearing sharp or poorly fitting dental appliances, or consuming very hot foods or drinks. The tissues in the mouth are delicate, making them more vulnerable to injury.
Some individuals may notice they develop blood blisters more easily than others. This can happen in people taking blood-thinning medications or in those with conditions that affect blood clotting or blood vessel strength. If blood blisters appear frequently without a clear cause, it may be wise to consult a healthcare professional for evaluation.
How to Care for a Blood Blister
In most cases, the safest approach is to leave the blister intact. The outer skin layer acts as a natural barrier that helps prevent infection. Popping or draining a blood blister can increase the risk of bacteria entering the area.
To support healing, keep the area clean and dry. Avoid additional pressure or friction. If the blister is located in a high-contact area, you can loosely cover it with a sterile bandage. If it is on your foot, wearing comfortable and properly fitting shoes can help reduce irritation.
If a blood blister breaks on its own, gently clean the area with mild soap and water. Apply a simple antiseptic and cover it with a sterile dressing while it heals.
When to Seek Medical Attention
Although most blood blisters heal without complications, you should consider seeking medical advice if you notice signs of infection. These may include increasing redness, warmth, swelling, pus, or worsening pain. A fever along with a blister should also be evaluated.
Professional care may also be appropriate if the blister is unusually large, extremely painful, slow to heal, or keeps coming back without an obvious cause.
Final Thoughts
A blood blister may look dramatic, but it is usually a temporary and manageable condition. With basic care and a little patience, most heal naturally without treatment.
Paying attention to changes in your skin and addressing irritation early can help prevent future blisters and protect your overall comfort.
