What is a pressure ulcer, and why does the category matter?
A pressure ulcer is localised damage to the skin and the tissue underneath, usually over a bony area such as the sacrum or heel. It is caused by pressure, or by pressure combined with shear. It can also form under a medical device, such as an oxygen mask or a catheter. Pressure ulcers happen in hospitals, care homes and people's own homes, and in people of every age, including babies.
Damage often begins deep, close to the bone, and may only show on the surface later. That is why a patient can look fine one day and have a serious ulcer a few days later.
Getting the category right matters for three reasons. It guides treatment and referral. It makes reporting reliable, so organisations can compare data and learn. And it gives the next nurse an accurate baseline, so any change can be spotted quickly.
What are the pressure ulcer categories?
The categories used in the UK are based on the international classification published by the European and US pressure ulcer advisory panels. The framework in England lists Categories 1 to 4 plus two extra groups: unstageable and deep tissue injury.
| Category | What you see | Key point |
|---|---|---|
| Category 1 | Intact skin with a localised area of redness that does not blanch when pressed | On darker skin, redness may not be visible. Look for colour change, warmth, coolness, firmness or pain |
| Category 2 | Partial-thickness skin loss: a shallow open wound with a red or pink base and no slough, or an intact or burst blister filled with clear fluid | A blood-filled blister is not Category 2. Think deep tissue injury |
| Category 3 | Full-thickness skin loss. Fat may be visible, but not bone, tendon or muscle | Slough may be present but does not hide the depth. There may be undermining or tunnelling |
| Category 4 | Full-thickness tissue loss with exposed bone, tendon or muscle | Slough or eschar may be present. High risk of infection, including osteomyelitis |
| Unstageable | Full-thickness loss where slough or eschar covers the base, so the depth cannot be seen | It is at least Category 3. The true category is only known once the base is visible |
| Suspected deep tissue injury | Purple or maroon intact skin, or a blood-filled blister, from damage in the deeper tissue | May feel boggy, firm, warm or cool. It can quickly evolve into a deeper wound |
Medical device related pressure ulcers
When pressure damage is caused by a device used for diagnosis or treatment, the national framework calls it a medical device related pressure ulcer. It is still categorised in the same way. Common sites are the bridge of the nose and the ears under oxygen masks and nasal cannulae, the nostril under a nasogastric tube, and skin under splints, casts, catheters and anti-embolism stockings.
How do you check for non-blanching redness, including on darker skin?
The blanching test is the main way to tell Category 1 damage from normal pressure redness. Press lightly on the red area with a finger for a few seconds, then release. If the skin goes pale and then turns red again, blood flow is intact. If it stays red, the tissue is damaged. Some teams use a clear plastic disc so they can see the skin while pressing.
On darker skin tones, redness and blanching can be very hard to see. Early damage may look purple, blue, grey or simply darker than the skin around it. Under-recognition of early damage in people with darker skin is a known problem, so take extra care.
- Use good light, ideally natural or a bright examination light.
- Compare the area with nearby skin that is not under pressure.
- Feel for warmth, coolness, firmness or a boggy texture.
- Ask the patient about pain, itching or discomfort at pressure points.
- Record what you felt and what the patient told you, not only what you saw.
What does SSKIN stand for?
SSKIN is a care bundle widely used across the UK to organise pressure ulcer prevention. Each letter is a prompt, and each element should be tailored to the person and written in their care plan.
| Letter | Element | What it looks like on the ward or at home |
|---|---|---|
| S | Surface | The right mattress, cushion and heel-offloading equipment for the person's level of risk. Check the equipment is working and correctly set up |
| S | Skin inspection | Regular checks of pressure areas and under devices. Record normal findings too, so a change is obvious |
| K | Keep moving | Repositioning to relieve pressure, using a 30-degree tilt and slide sheets to reduce shear. Encourage people who can move to do so |
| I | Incontinence and moisture | Prompt cleansing, barrier products and suitable continence aids. Tell moisture damage apart from pressure damage |
| N | Nutrition and hydration | Nutritional screening such as MUST, food and fluid monitoring, and dietitian referral when needed |
What is aSSKINg?
Many organisations now use an extended version called aSSKINg. The small a stands for assess risk, and the g stands for giving information. The extra letters remind you that prevention starts with a proper risk assessment and that patients, families and carers need clear information so they can take part in their own care, especially at home.
How often should patients be repositioned?
NICE guideline CG179 advises encouraging adults at risk to change position at least every 6 hours, and at least every 4 hours for those at high risk. These are minimums. Many patients need more frequent changes, based on their skin checks, comfort and condition. Follow the individual plan and your local policy, and check the current NICE guidance for children and neonates, which has its own recommendations.
Who needs a risk assessment, and when?
NICE recommends a pressure ulcer risk assessment for adults admitted to hospital or to care homes where NHS care is provided, and for people in other settings who have risk factors. NICE quality standard QS89 states that people admitted to hospital or a care home with nursing should be assessed within 6 hours of admission. In the community, assess at the first visit if risk factors are present. Repeat the assessment whenever the person's condition changes.
Tools such as Waterlow, Braden and Purpose-T support clinical judgement but do not replace it. A score just under the threshold does not make a patient safe if you can see they cannot move themselves.
- Reduced mobility, for example after surgery, a stroke, sedation or an epidural.
- A previous or current pressure ulcer.
- Poor nutrition, dehydration or recent weight loss.
- Incontinence or heavy sweating.
- Reduced sensation, poor circulation or diabetes.
- Cognitive impairment or delirium.
- Serious acute illness, including sepsis.
- Medical devices in contact with the skin.
Waterlow 16. High risk. Continue care.
Purpose-T repeated at the bedside at 10:15 after return from theatre. Now high risk: new epidural, reduced sensation in both legs, unable to reposition. Sacrum has blanching redness, heels intact. Plan updated: dynamic mattress requested, heels offloaded, skin check at every repositioning, repositioning at least every 4 hours and more often if the skin changes. Patient informed and agrees.
Worked example: categorising and planning care
Joseph is drowsy, has been in bed at home for several days and has urinary incontinence. On the admission skin check the nurse finds a shallow pink wound on the sacrum, about 2 cm across, with no slough. There is also an intact purple area on his left heel that feels boggy. His skin is dark, and the nurse uses a bright light and compares both heels by touch.
- Categorise each area: The sacral wound is Category 2: partial-thickness loss, pink base, no slough. The heel is a suspected deep tissue injury: intact discoloured skin that is boggy to touch.
- Decide where it came from: Both were seen at the admission skin assessment, so both are recorded as present on admission. The national framework has abandoned the old 72-hour rule.
- Put SSKIN in place: Pressure-redistributing mattress, heels fully offloaded, skin checks at each repositioning, regular repositioning avoiding the sacrum, barrier product and continence care, MUST screen and dietitian referral.
- Escalate and report: Refer the deep tissue injury to tissue viability in line with local policy, inform the medical team, and complete an incident report for both areas.
- Document and inform: Record size, appearance, pain, photographs taken with consent if your policy allows, and the plan. Explain the findings and plan to Joseph and his family.
How should pressure ulcers be documented and reported?
Report pressure ulcers on your organisation's incident reporting system, whether they developed in your care or were present on admission. In England, local systems feed the national Learn from Patient Safety Events service. The 2018 framework also asks organisations to review new damage to understand how it happened and what can be learned, and it advises against labelling ulcers as avoidable or unavoidable.
- Record the site, category, size, wound bed, exudate, surrounding skin and pain.
- State whether it was present on admission or developed during this episode of care.
- Record the prevention plan and any changes to it.
- Refer Category 3, Category 4, unstageable and deep tissue injuries to tissue viability in line with local policy.
- Tell the patient and their family what you found, and if harm happened in your care, apologise and explain what is being done.
Openness is a professional duty under the NMC Code and the joint GMC and NMC guidance on candour. Where harm meets the threshold for the statutory duty of candour, your organisation's process will also apply. Most pressure ulcers are not caused by abuse or neglect, but severe or multiple ulcers may raise safeguarding questions, including self-neglect. Follow local safeguarding policy and talk to your safeguarding lead if unsure.
Building confidence in prevention and categorisation
Pressure ulcer prevention is not complicated, but it depends on doing simple things reliably on every shift: assessing risk, looking at the skin, acting on what you find and writing it down. Most learning after incidents comes back to these basics, often with a busy shift, a confused patient or a missed heel check in the background.
If you want structured practice, our course Pressure Ulcer Prevention and Reporting covers risk assessment, SSKIN planning, categorisation (including on darker skin), documentation and a reflective case study. It can support your CPD or revalidation, or a reflection after an incident. Whatever you choose, keep using your local policy and current NICE guidance as your first reference.
Frequently asked questions
What are the 4 categories of pressure ulcers?
Category 1 is non-blanching redness on intact skin. Category 2 is partial-thickness skin loss or a clear fluid blister. Category 3 is full-thickness skin loss where fat may show but not bone, tendon or muscle. Category 4 is full-thickness loss with exposed bone, tendon or muscle. The UK also uses unstageable and suspected deep tissue injury.
What does SSKIN stand for in nursing?
SSKIN stands for Surface, Skin inspection, Keep moving, Incontinence and moisture, and Nutrition and hydration. It is a prevention bundle used across the UK to make sure each part of pressure ulcer prevention is planned, delivered and recorded for every person at risk.
What is the difference between SSKIN and aSSKINg?
aSSKINg adds two elements to SSKIN. The a stands for assess risk and the g stands for giving information. They remind staff that prevention starts with a proper risk assessment and that patients, families and carers need clear information to take part in their care.
Is a blister a Category 2 pressure ulcer?
An intact or burst blister filled with clear fluid over a pressure area is usually Category 2. A blood-filled blister is different. It suggests damage in the deeper tissue and should be recorded as a suspected deep tissue injury, then monitored closely because it can evolve into a deeper wound.
Can a pressure ulcer go down a category as it heals?
No. Pressure ulcers are not reverse-categorised. A Category 3 ulcer that is healing remains a Category 3 ulcer, described as healing. Record the original category, the measurements and the changes you see, so progress can be tracked accurately.
How do you spot a Category 1 pressure ulcer on dark skin?
Redness may not be visible, so rely on more than sight. Use good light, compare with nearby skin, and feel for warmth, coolness, firmness or bogginess. The area may look purple, blue or darker than surrounding skin. Ask the patient about pain or discomfort and record what you find.
How often should a patient at risk be repositioned?
NICE CG179 advises encouraging adults at risk to change position at least every 6 hours, and at least every 4 hours if they are at high risk. These are minimums. Many patients need more frequent repositioning based on skin checks and their condition, so follow the individual plan and local policy.
Related courses
Pressure Ulcer Prevention and Reporting
This course teaches nurses and midwives how to identify people at risk of pressure ulcers, deliver prevention using the SSKIN bundle, categorise…
Maternity Care and Fetal Monitoring Concerns
This course teaches safe fetal monitoring in labour, including intermittent auscultation, structured CTG review and escalation, using UK guidance and…
Paramedic Practice: Assessment and Non-Conveyance Decisions
This course teaches a structured approach to assessment and safe decision-making when a paramedic considers discharging a patient on scene or…
Sources and further reading
- Pressure ulcers: prevention and management (CG179). National Institute for Health and Care Excellence.
- Pressure ulcers (Quality Standard QS89). National Institute for Health and Care Excellence.
- Pressure ulcers: revised definition and measurement framework. NHS England (formerly NHS Improvement).
- Guidance for reporting pressure ulcers. NHS England (formerly NHS Improvement).
- The Code: Professional standards of practice and behaviour for nurses, midwives and nursing associates. Nursing and Midwifery Council.
- Openness and honesty when things go wrong: the professional duty of candour. General Medical Council and Nursing and Midwifery Council.
Practitioner Insight is an independent education provider. It is not affiliated with or endorsed by the GMC, MPTS, NMC, HCPC, GPhC or any NHS organisation, and this information is not legal advice. If you have been referred to a regulator, speak to your defence organisation, trade union or legal representative.
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