A bed sore can look very different depending on how far it has progressed. In its earliest form, it appears as a patch of red or discolored skin that doesn’t fade when you press on it. As it worsens, it can develop into an open wound, a blister, or eventually a deep crater exposing fat, muscle, or even bone. Knowing what each stage looks like helps you catch the problem early, when it’s easiest to treat.
Where Bed Sores Typically Appear
Bed sores form over bony areas where skin gets compressed between the bone and a mattress or chair. They develop in areas that don’t have much muscle or fat for cushioning. For someone who is mostly in bed, the most common spots are the tailbone, heels, shoulder blades, hips, lower back, ankles, the skin behind the knees, and the back or sides of the head. For wheelchair users, they tend to show up on the tailbone and buttocks, the shoulder blades and spine, and the backs of the arms and legs where they press against the chair.
If you’re checking someone’s skin for early signs, these bony prominences are the places to look first.
Stage 1: Skin Is Intact but Discolored
The earliest bed sore doesn’t look like a wound at all. The skin stays intact, but you’ll notice a localized area of redness over a bony spot that doesn’t go away. Normally, if you press on reddened skin with your finger, it briefly turns white (blanches) and then returns to its usual color. With a Stage 1 bed sore, the redness stays put when you press on it. This is called non-blanchable redness, and it’s the hallmark of this stage. The discoloration typically persists for more than 20 minutes after pressure is relieved.
Beyond color, the skin may feel different from the surrounding area. It can be warmer or cooler to the touch, firmer, softer, or slightly swollen. Some people report pain or itching at the spot before any visible change appears.
What Stage 1 Looks Like on Darker Skin
On darker skin tones, redness is often invisible. Instead, the area may appear purple, blue, or violet. The skin might also look ashy or have a noticeably different shade compared to the tissue around it. Researchers at the University of Wisconsin have emphasized that purple discoloration on dark skin is a critical warning sign, one that is frequently mistaken for a simple bruise. The tissue underneath may feel “boggy” or waterlogged, and temperature differences (warmer or cooler than the surrounding skin) become especially important clues when color changes are hard to see.
Stage 2: Shallow Open Wound or Blister
At Stage 2, the top layers of skin have broken down. What you’ll see is a shallow, open sore with a red or pink wound bed. It looks raw, similar to a scrape or a popped blister. There’s no thick yellow or black tissue covering it at this stage. It can also appear as an intact, fluid-filled blister or one that has already ruptured and is weeping clear fluid. The area around the sore may be tender and swollen. This is still a relatively superficial injury, but it signals that the damage is progressing and needs attention.
Stage 3: A Deeper Crater
A Stage 3 bed sore is a full-thickness wound, meaning the damage extends through all layers of skin and into the fat underneath. It typically looks like a crater or a deep bowl-shaped hole. You may be able to see yellowish fatty tissue at the base of the wound. The edges of the sore can roll inward or develop tunnels that extend under the surrounding skin, making the wound larger beneath the surface than it appears at the opening. Bone, tendon, and muscle are not yet visible at this stage, but the wound is clearly deep and serious.
Stage 4: Bone or Muscle Is Exposed
This is the most severe stage. A Stage 4 bed sore is a large, deep wound where tissue destruction reaches down to muscle, tendon, or bone. You may be able to see these structures directly at the base of the wound. The sore often has dead tissue that is dark or discolored along the edges. Tunneling and undermining (where the wound extends sideways beneath intact skin) are common, so the true size of the injury is often much larger than the visible opening suggests. These wounds carry a high risk of life-threatening infection.
Unstageable Sores: When You Can’t Tell How Deep It Is
Sometimes a bed sore is covered by a layer of dead tissue that hides the wound bed, making it impossible to determine the true depth. This covering comes in two forms. Slough is soft, moist dead tissue that can appear yellow, tan, grey, green, or brown. Eschar is harder and drier, looking tan, brown, or black, almost like a thick scab or a leathery patch. Until this dead tissue is removed and the base of the wound is visible, the actual stage of the sore can’t be determined. An unstageable wound is always at least a Stage 3 or worse underneath.
Deep Tissue Injury: Damage From the Inside Out
A deep tissue pressure injury is a unique and sometimes deceptive type. The skin may still be intact, but the tissue underneath has been severely damaged by sustained pressure. It typically appears as a dark purple or maroon patch of discolored skin, or as a blood-filled blister. The area often feels firmer, mushier, warmer, or cooler than the surrounding skin. What makes this type dangerous is that the visible surface can look relatively mild while significant destruction is happening in the deeper layers of tissue. Over the following days, the wound can rapidly deteriorate and open up, revealing the full extent of the damage beneath.
Signs a Bed Sore May Be Infected
Any open bed sore can become infected, and the visual signs are important to recognize. Watch for increasing redness or warmth spreading outward from the wound edges, swelling that wasn’t there before, and discharge that is green, yellow, or has a foul smell. The wound bed itself may change color or develop new areas of dark or grey tissue. Fever, increased pain, and a general feeling of being unwell alongside these wound changes can signal that the infection is spreading beyond the sore itself into the surrounding tissue or bloodstream.
How Quickly the Appearance Changes
Bed sores can progress from a Stage 1 discoloration to an open wound in a matter of hours or days, especially in people with poor circulation, diabetes, or limited sensation who can’t feel the pain that would normally prompt them to shift position. A deep tissue injury can look like a bruise one day and break open into a Stage 3 or 4 wound within a week. This speed is why daily skin checks over bony areas matter so much for anyone with limited mobility. Catching a persistent red or purple patch early, when the skin is still intact, gives the best chance of reversing the damage simply by relieving the pressure.