Cellulitis develops when bacteria enter through a break in the skin and infect the deeper layers beneath the surface. The break doesn’t have to be dramatic. Something as minor as cracked skin between your toes from athlete’s foot, a small scratch, or even dry, flaky skin from eczema can be enough to let bacteria in. Once inside, the infection spreads through the tissue, causing redness, swelling, warmth, and pain that typically expands outward from the entry point.
The Bacteria Behind It
Two types of bacteria cause the vast majority of cellulitis cases in otherwise healthy people: group A streptococcus and Staphylococcus aureus. Which one is more likely depends on the circumstances. When cellulitis appears on intact-looking skin with no obvious wound, drainage, or abscess, streptococcus is the most common culprit. When there’s a visible wound, puncture, or abscess involved, Staphylococcus aureus is more likely, including community-acquired MRSA strains.
Certain situations introduce less common bacteria. Animal and human bites cause infections that are usually polymicrobial, meaning multiple bacterial species are involved at once. Dog bites carry different organisms than cat bites or human bites. Puncture wounds that happen in water, whether an ocean, lake, or stream, can introduce bacteria rarely found on land. And people with weakened immune systems can develop cellulitis from a broader range of bacteria that wouldn’t normally cause infection in healthy individuals.
How Bacteria Get Through the Skin
Your skin is a physical barrier that keeps bacteria out. Cellulitis requires a breach in that barrier, though the opening can be so small you never notice it. The most common entry points include:
- Cuts, scrapes, and puncture wounds, including surgical incisions, tattoos, and piercings
- Chronic skin conditions like eczema, athlete’s foot, and psoriasis that create persistent cracks or raw patches
- Blisters from burns, shingles, or chickenpox
- Insect bites or animal bites
- Ulcers, particularly on the lower legs
- Injection drug use
- Dry, cracked skin, especially on the feet and lower legs
Athlete’s foot deserves special attention because it’s one of the most overlooked entry points. The fungal infection creates small fissures in the skin between the toes, and bacteria can slip through those cracks and travel up into the leg. Since cellulitis occurs most often on the lower legs, this connection matters more than most people realize.
Why the Lower Legs Are Most Affected
Cellulitis can develop anywhere on the body, but the lower legs are by far the most common location. Several factors converge there. Gravity pulls fluid downward, which can cause swelling and stretch the skin. Circulation is naturally weaker in the lower extremities, making it harder for your immune system to respond quickly. The feet and legs are also more exposed to minor injuries, fungal infections, and insect bites than most other body parts.
People with poor circulation in their legs, whether from varicose veins, venous insufficiency, or simply spending long hours standing, face a higher risk. The combination of sluggish blood flow and minor skin damage creates conditions where bacteria can establish an infection before the body mounts an effective defense.
Risk Factors That Raise Your Chances
Lymphedema and Swelling
Lymphedema, a condition where fluid accumulates in tissue because the lymphatic system isn’t draining properly, is one of the strongest risk factors for cellulitis. The lymphatic system normally helps clear bacteria and waste from tissue. When it’s compromised, fluid pools under the skin, the tissue becomes swollen, and the immune response in that area weakens. Research shows that the greater the swelling (measured by circumference difference between the affected and unaffected limb), the higher the risk of developing cellulitis. Lymphedema can result from surgery, particularly when lymph nodes are removed during cancer treatment such as mastectomy, or from radiation therapy, chronic infections, or inherited conditions.
Obesity
Carrying excess weight significantly increases the risk of cellulitis through several interconnected pathways. Fat tissue that outgrows its blood supply becomes oxygen-deprived, which triggers chronic low-level inflammation throughout the body. Over time, this persistent inflammation exhausts immune cells. Macrophages, the white blood cells that normally engulf and destroy bacteria, show reduced ability to clear infections in people with obesity. T cells, which coordinate the immune response, become less effective and less diverse in the types of threats they can recognize. The body’s ability to produce new immune cells also diminishes under constant inflammatory stress, creating a compounding effect where the immune system progressively weakens.
Obesity also causes skin folds that trap moisture and create friction, both of which damage the skin barrier and encourage bacterial growth.
Diabetes
Diabetes increases cellulitis risk through poor circulation, reduced nerve sensation (which means injuries go unnoticed longer), and impaired immune function. High blood sugar interferes with white blood cell activity, slowing the body’s ability to fight off infections once bacteria have entered the skin.
Previous Cellulitis
Having cellulitis once makes you more likely to get it again. Each episode of infection can damage the lymphatic vessels in the affected area, reducing drainage capacity and creating conditions favorable for reinfection. This is why some people experience repeated bouts of cellulitis in the same limb, with each episode further compromising the lymphatic system and increasing the likelihood of the next one.
What the Infection Looks and Feels Like
Cellulitis typically appears as an area of red, swollen skin that feels hot and tender to the touch. The redness spreads over hours to days, and the borders are usually not sharply defined. You might notice the affected area growing visibly larger if you track its edges. Many people also develop a fever, chills, or a general feeling of being unwell as the infection progresses.
The skin may look tight or glossy from swelling. In some cases, small blisters or dimpling (sometimes described as an orange-peel texture) appear on the surface. The pain tends to be constant rather than sharp, and the area is usually painful to press on. Unlike a superficial wound infection that stays localized, cellulitis spreads through deeper tissue layers, so the area of redness and pain is often much larger than the original wound.
How Cellulitis Is Different From an Abscess
People sometimes confuse cellulitis with a skin abscess, but they behave differently. An abscess is a contained pocket of pus, often with a firm, raised center that may eventually drain on its own. Cellulitis is a spreading infection without a defined pocket of fluid. That said, an abscess can cause surrounding cellulitis, and cellulitis can sometimes progress to form an abscess. The distinction matters because the treatment approach differs: abscesses typically need to be drained, while cellulitis is treated with antibiotics alone.
How Common It Is
Cellulitis is one of the most frequent reasons for antibiotic prescriptions and hospital admissions related to skin infections. One population-based study estimated an incidence of roughly 24.9 cases per 1,000 person-years, which makes it remarkably common. It affects people of all ages, though older adults and those with the risk factors described above carry a disproportionate burden.
Reducing Your Risk
Since cellulitis begins with bacteria entering broken skin, the most effective prevention centers on protecting your skin barrier. Keep wounds clean and covered until they heal. Moisturize dry, cracking skin on your legs and feet daily, especially in winter. Treat athlete’s foot promptly rather than ignoring it. If you have eczema or another chronic skin condition, managing flares helps reduce the number of openings bacteria can exploit.
For people with lymphedema, compression garments help control swelling and maintain healthier tissue. Keeping swelling to a minimum directly reduces cellulitis risk. If you’ve had previous episodes of cellulitis, paying close attention to any skin breaks on the affected limb and treating minor injuries quickly can help interrupt the cycle of recurrent infection.