Pressure sores - What is a pressure sore?
BMJ Group Medical Reference
Anyone can get a pressure sore if they sit or lie still for too long without moving. People who are old or very ill are particularly likely to get pressure sores. Careful nursing, special beds, and foam mattresses can all help protect your skin, and stop a pressure sore from developing.
We've brought together the best research about pressure sores and weighed up the evidence about how to prevent and treat them. If you think that you might be at risk of getting pressure sores, you can use our information to talk to your doctor and decide which treatments are best.
Pressure sores are areas of damaged or broken skin. People who are ill who sit or lie in one position for too long can get them quite quickly. Without treatment, they can become deep wounds that take a long time to heal.
When you sit or lie down you naturally shift your position from time to time, even when you're asleep.
But if you can't move yourself because you are too ill or weak, or even unconscious, you could get a pressure sore.
Experts think pressure sores start when:
The weight of your body presses down on the skin underneath. This pressure stops your blood from circulating properly through the skin, so the skin doesn't get enough oxygen or nutrients. If you don't shift your position, the skin cells die and the skin breaks down
The layers of your skin slide over each other as you slip down or are pulled up in bed. This is called shearing
Your skin is dragged across the mattress or seat as someone moves you. This is called friction.
Pressure, shearing, and friction all damage your skin and increase the chance of a pressure sore. Areas of skin over the bony parts of your body are most at risk. 
Anyone who has difficulty moving can get a pressure sore. But you are more likely to get one if you:
Are very old or very young
Are seriously ill, drowsy, or unconscious
Have had surgery
Can't control urine or faeces
Have a serious injury, such as a broken hip
Are very overweight (obese)
Don't eat or drink enough
Have poor circulation, perhaps because you smoke
Have had a pressure sore before
Can't feel pain. This can happen if your spinal cord is injured, or if diabetes has damaged your nerves.
Diabetes is a condition that causes too much sugar (glucose) to circulate in the blood. It happens when the body stops making a hormone called insulin (type 1 diabetes) or when insulin stops working (type 2 diabetes).
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