Learn how bed sores start, why pressure wounds worsen, early warning signs, and when pressure injuries need medical care.
Written and medically reviewed by Stephanie Wright, RN, BSN
Bed sores, also called pressure wounds or pressure injuries, develop when constant pressure limits blood flow to the skin. Without enough blood, skin and underlying tissue do not receive the oxygen and nutrients they need to stay healthy. Over time, this leads to tissue damage and breakdown.
Many people think bed sores only occur in hospitals or nursing homes. In reality, they can develop anywhere a person spends long periods sitting or lying in one position. Bed sores can affect people at home, in long-term care, or during recovery from illness or surgery.
Understanding how bed sores start and why they worsen helps patients, families, and caregivers take action early. Early pressure wounds are often reversible. Advanced bed sores are much harder to treat and carry a higher risk of infection and complications.
This guide explains what causes bed sores, the earliest warning signs, why pressure wounds don’t heal easily, and how infection develops in pressure injuries.
What Causes Bed Sores
Bed sores form when pressure reduces blood flow to the skin for too long. Blood delivers oxygen and nutrients that keep tissue alive. When pressure blocks blood flow, tissue becomes damaged.
Pressure does not have to be extreme. Even moderate pressure can cause injury if it lasts long enough.
Common causes of bed sores include:
- Remaining in one position for long periods
- Limited mobility or paralysis
- Poor circulation
- Reduced sensation
- Moisture from sweat or incontinence
Pressure wounds most often form over bony areas where there is less padding between skin and bone, such as the heels, tailbone, hips, elbows, and ankles.
Once tissue damage begins, the wound can worsen quickly if pressure is not relieved.
Early Signs of Pressure Wounds
Early pressure wounds often look mild at first. Because the skin may still be intact, these signs are easy to miss. Understanding how bed sores start helps patients and caregivers prevent pressure wounds before they become severe.
When pressure wounds are caught early, serious damage can often be prevented.
Skin Changes to Watch For
The skin may appear different from surrounding areas. Changes may include:
- Redness in lighter skin tones
- Purple, blue, or darkened skin in darker skin tones
- Skin that does not turn white when pressed
- Shiny or tight-looking skin
A key warning sign is non-blanchable skin, meaning the color does not fade when pressure is applied.
Temperature and Texture Changes
Early pressure damage may also cause:
- Skin that feels warmer or cooler than nearby skin
- Firm or spongy texture
- Mild swelling
These changes suggest inflammation or fluid buildup under the skin.
Immobility
Immobility is one of the strongest risk factors for bed sores. When a person cannot change position easily, pressure remains in the same area for too long.
People at higher risk include those who:
- Are on prolonged bed rest
- Use wheelchairs
- Have paralysis or severe weakness
- Are recovering from surgery or serious illness
Even small movements help relieve pressure. When movement is limited, pressure builds quickly and tissue damage begins below the surface.
Immobility also makes it harder for people to notice early warning signs. This allows pressure wounds to worsen quietly.
Pressure and Friction
Pressure is the main cause of bed sores, but friction often makes them worse.
Pressure cuts off blood flow. Friction damages the outer layer of skin. When both occur together, the risk of skin breakdown increases.
Common sources of friction include:
- Sliding down in bed
- Dragging skin across sheets
- Poor positioning
- Improper transfer techniques
Friction weakens the skin’s protective barrier, making it easier for pressure damage to progress into deeper tissue.
Skin Breakdown
Skin breakdown happens when the skin’s natural defenses fail. Pressure, friction, and moisture all contribute to this process.
Moisture from sweat, urine, or stool softens the skin. Soft skin tears more easily and cannot protect underlying tissue.
Once skin breaks open:
- Healing becomes slower
- Infection risk increases
- Pain and complications are more likely
Skin breakdown marks a turning point in pressure wound severity and often signals the need for medical care.
Why Bed Sores Don’t Heal Easily
Pressure wounds heal differently than simple cuts or scrapes. Several factors make healing more difficult.
First, pressure often continues even after a wound forms. Ongoing pressure prevents blood flow and slows repair.
Second, damaged tissue beneath the skin may be more extensive than it appears on the surface. This hidden damage delays healing.
Third, many people with bed sores also have:
- Poor circulation
- Poor nutrition
- Chronic illness
- Reduced immune function
These factors limit the body’s ability to rebuild tissue and fight bacteria.
Once a pressure wound progresses beyond early stages, healing becomes slower and more complex.
How Blood Flow Loss Affects Skin and Tissue
Pressure wounds do not begin at the surface. Damage starts when pressure reduces blood flow to the skin for too long. Without blood, tissue loses oxygen and nutrients needed to survive.
When blood flow is restricted:
- Cells become stressed and weak
- Waste products build up
- Tissue repair slows or stops
This process can begin within hours. The longer pressure continues, the more tissue is affected. That is why even short periods of immobility can be harmful in people who are already vulnerable.
Blood flow loss also explains why bed sores often worsen quickly once they begin. The body cannot repair tissue that is not being supplied with oxygen.
Why Bed Sores Often Look Worse Than They Feel
Many people expect bed sores to be painful right away. In reality, pain may be mild or absent in the early stages.
This happens because:
- Nerves may be damaged or compressed
- Tissue damage occurs beneath the surface
- Sensation may already be reduced
As a result, a wound can progress even when discomfort is minimal. This makes regular skin checks more important than relying on pain alone.
A lack of pain does not mean the wound is improving.
How Pressure Wounds Damage Deep Tissue First
One of the most misunderstood aspects of bed sores is how they spread. Pressure wounds often damage muscle and fat before the skin opens.
This happens because:
- Muscle needs more oxygen than skin
- Pressure affects deeper layers more intensely
- Skin may stay intact while tissue underneath breaks down
When the skin finally opens, the damage underneath may already be extensive. This makes healing slower and increases the risk of complications.
Understanding this hidden progression helps explain why early pressure relief is critical.
Moisture and Skin Breakdown
Moisture does not cause bed sores on its own, but it makes skin much more vulnerable to pressure damage.
Sources of moisture include:
- Sweat
- Urine or stool
- Wound drainage
- Damp bedding or clothing
Moist skin:
- Softens easily
- Tears more quickly
- Loses its protective barrier
When moisture combines with pressure and friction, skin breakdown accelerates. Managing moisture is a key part of preventing wounds from worsening.
Why Nutrition Plays a Role in Healing
Healing requires energy and building materials. When nutrition is poor, the body struggles to repair damaged tissue.
People at higher risk include those who:
- Eat very little
- Lose weight unintentionally
- Have difficulty swallowing
- Are dehydrated
Important nutrients for healing include:
- Protein
- Calories
- Fluids
- Vitamins and minerals
Nutrition alone cannot heal bed sores, but without it, healing becomes much harder.
How Bed Sores Progress Without Treatment
Understanding progression helps patients and caregivers recognize urgency.
Early Pressure Damage
- Skin remains intact
- Color or texture changes appear
- Damage is mostly beneath the surface
Moderate Pressure Injury
- Skin opens or blisters
- Drainage may begin
- Pain and swelling increase
Advanced Pressure Injury
- Deep ulcers form
- Muscle or bone may be involved
- Infection risk is high
The earlier treatment begins, the easier it is to stop this progression.
Why Bed Sores Worsen Over Time
| Factor | Early Stage | Advanced Stage |
| Blood flow | Reduced but present | Severely limited |
| Skin surface | Intact | Open or ulcerated |
| Tissue damage | Shallow | Deep, involving muscle or bone |
| Infection risk | Low | High |
Healing difficulty Often reversible Complex and prolonged
How Bed Sores Affect Overall Health
Bed sores don’t just affect the skin. When pressure wounds worsen, they can strain the entire body. Ongoing tissue damage increases inflammation and makes healing harder everywhere else. The body has to divide its energy between fighting injury and managing other health needs.
In people who are already ill, bed sores can slow recovery and reduce strength. Pain, limited movement, and infection risk can lead to longer hospital stays and greater dependence on caregivers. Sleep may suffer, and appetite may decrease, which further interferes with healing. Because of this, preventing bed sores helps protect more than skin health. Early action supports mobility, comfort, and overall well-being—especially in older adults and people with chronic conditions.
Why Repositioning Is So Effective
Repositioning is one of the simplest and most effective ways to prevent bed sores from worsening.
Changing position:
- Restores blood flow
- Reduces pressure points
- Allows tissue to recover
For people in bed, repositioning every two hours is often recommended. For people in chairs or wheelchairs, frequent weight shifts are important.
Even small movements make a difference.
Why Support Surfaces Matter
Mattresses and cushions designed to reduce pressure can significantly lower bed sore risk.
Support surfaces work by:
- Distributing weight more evenly
- Reducing pressure on bony areas
- Improving comfort and circulation
These tools do not replace repositioning, but they support skin health and reduce strain.
Why Bed Sores Can Return After Healing
Once a bed sore heals, the area remains more fragile.
Scar tissue:
- Is less flexible
- Breaks down more easily
- Tolerates pressure poorly
This is why prevention must continue even after healing. Ongoing skin checks and pressure relief remain important.
What Patients and Families Can Do Daily
Daily habits have a major impact on pressure wound outcomes.
Helpful steps include:
- Checking skin every day
- Noticing color, texture, or temperature changes
- Keeping skin clean and dry
- Encouraging movement when possible
- Speaking up early about concerns
Education and consistency prevent many serious wounds.
Why Early Action Prevents Serious Complications
Most severe bed sores begin as small, manageable changes. Acting early prevents:
- Deep tissue damage
- Infection
- Hospitalization
- Long-term disability
Early action protects both skin health and overall quality of life.
Infection Risks in Pressure Wounds
Infection is one of the most serious complications of bed sores.
Open or damaged skin allows bacteria to enter the wound. Pressure wounds often remain moist and poorly oxygenated, which encourages bacterial growth.
Signs of infection may include:
- Increasing redness or warmth
- Drainage or pus
- Foul odor
- Fever or chills
- Delayed healing
Infection can spread beyond the wound into deeper tissue, muscle, or bone. In severe cases, it can enter the bloodstream and become life-threatening.
Early recognition and treatment of infection are critical to preventing serious outcomes.
How Bed Sores Progress Over Time
Understanding how bed sores worsen helps explain why early care matters so much.
Early Stage
- Skin is intact
- Color or texture changes appear
- Damage is mostly below the surface
Intermediate Stage
- Skin opens or blisters
- Drainage may appear
- Tissue damage deepens
Advanced Stage
- Deep ulcers form
- Muscle or bone may be exposed
- Infection risk is high
The longer pressure continues, the harder it becomes to reverse damage.
Why Some Bed Sores Worsen Faster Than Others Not all bed sores progress at the same rate.
Factors that speed progression include:
- Poor circulation
- Diabetes
- Malnutrition
- Dehydration
- Infection
- Reduced sensation
People who cannot feel discomfort may not shift position naturally. Without this feedback, pressure remains unrelieved and damage worsens.
The Role of Prevention
Prevention is the most effective way to manage bed sores.
Key prevention strategies include:
- Repositioning regularly
- Using pressure-relieving surfaces
- Keeping skin clean and dry
- Supporting nutrition and hydration
- Checking skin daily
Education and routine care reduce the risk of severe pressure wounds.
When to Get Help
Medical evaluation is important when:
- Skin discoloration does not improve
- Blisters or open wounds appear
- Drainage or odor develops
- Pain, swelling, or fever occurs
- Healing stalls or worsens
Waiting too long allows manageable wounds to become serious injuries.
Key Takeaway
Bed sores start when pressure blocks blood flow to the skin. They worsen when pressure continues, skin breaks down, and infection develops.
Early signs are often subtle, but early action makes a major difference. Relieving pressure and protecting the skin at the first warning signs can prevent serious wounds and complications.
Concerned About Pressure Wounds?
If you or someone you care for is at risk for bed sores or has a wound that isn’t improving, learning how pressure wounds develop can help prevent serious injury. Get clear guidance on pressure wounds and when medical care is needed.
References:
- Cleveland Clinic. (2023, February 24). Bedsores (pressure injuries). Cleveland Clinic.
- Shi, C., Bonnett, L. J., Dumville, J. C., & Cullum, N. (2020). Nonblanchable erythema for predicting pressure ulcer development: a systematic review with an individual participant data meta-analysis. The British journal of dermatology, 182(2), 278–286.
- Ahmad, B., Rubio-Sefati, M., & Yacob, M. M. (2023). Incidence and risk factors for pressure injuries in patients who have undergone vascular operations: a scoping review. European journal of medical research, 28(1), 77.
- Gould, L. J., et al. (2024). WHS guidelines for the treatment of pressure ulcers — 2023 update. Wound Repair and Regeneration.
- Boyko, T. V. (2018). Review of the current management of pressure ulcers. Journal of Wound Care.
- Saghaleini, S. H., Dehghan, K., Shadvar, K., Sanaie, S., Mahmoodpoor, A., & Ostadi, Z. (2018). Pressure Ulcer and Nutrition. Indian journal of critical care medicine : peer-reviewed, official publication of Indian Society of Critical Care Medicine, 22(4), 283–289.
- Johns Hopkins Medicine. (n.d.). Bedsores (pressure injuries). Johns Hopkins Medicine.
