Purple is one of the more significant wound colors, and it shows up in two situations that both call for action.
As a deep tissue injury. Some pressure sores develop in the tissue deep below the skin. The area may be dark purple or maroon, and there may be a blood-filled blister under the skin. Here’s why this one matters: this type of skin injury can quickly become a stage III or IV pressure sore.
Quickly — and stage III and IV sores are harder to treat and slow to heal. The skin above may still be unbroken.
As a sign about healing. With foot ulcers, wounds that are pale, purple, or black are less likely to heal, and after debridement the wound should be red or pink. There’s also a separate instruction: contact your provider if your foot ulcer is very white, blue, or black.
Discoloration on a leg is different again, and slower. Dark red, purple, brown, hardened skin is one of the early signs of venous insufficiency, and it’s a sign that blood is pooling. That one develops over months and sits on intact skin away from any wound.
So the question that separates them is where and how fast. A dark purple or maroon patch over a bony area in someone who spends long periods in a bed or chair is the deep tissue injury described above. Gradual purple-brown discoloration on a lower leg is the venous kind.
Neither is something to watch for a few days. The first can become severe quickly; the second is a sign of a condition that leads to ulcers.