A bacterial infection skin concern may cause redness, warmth, swelling, pain, or drainage, but several nonbacterial conditions can look similar.
This DermOnDemand guide cites Dr. Alicia Atkins, MD, FAAD, a fellowship-trained dermatology expert. It explains common types of infections, their causes, diagnosis, treatment options, and signs that require in-person care.
Key Takeaways
- Bacterial skin infections often cause redness, warmth, swelling, pain, crusting, drainage, or pus-filled bumps, but other skin conditions can look similar.
- Common types include cellulitis, impetigo, folliculitis, boils, abscesses, and erysipelas, each affecting the skin differently.
- Treatment may involve topical or oral antibiotics, while abscesses often require professional drainage.
- Rapidly spreading redness, fever, severe pain, eye-area swelling, or unusual skin color changes require prompt medical evaluation.
- Clean wound care, handwashing, covered drainage, and avoiding shared personal items can reduce the risk of infection and transmission.
What Is a Bacterial Skin Infection?
A bacterial skin infection develops when harmful bacteria enter the skin and multiply. A skin infection caused by bacteria may remain near the surface or spread into deeper skin and soft tissue. Common bacterial skin infections include impetigo, folliculitis, cellulitis, erysipelas, boils, and abscesses.
Colonization Versus Active Infection
Some bacteria live on healthy skin or inside the nose and mouth without causing symptoms. This is called colonization, and it does not always require treatment. An active infection causes inflammation, tissue damage, or symptoms such as pain, swelling, warmth, crusting, or pus.
How to Tell if It Is Bacterial
You cannot always identify the cause of a rash by appearance alone. A clinician considers the location, symptoms, speed of spread, recent injuries, medical history, and possible exposure. Testing may be needed when the diagnosis is unclear or the condition does not respond to initial care.
Bacterial Infection Skin Rash Symptoms
A bacterial infection skin rash may appear red, swollen, warm, tender, or crusted. Some infections form blisters, open sores, or pus-filled bumps. Signs vary based on the organism, the depth of infection, and the area of the body involved.
Common signs include:
- Increasing redness, warmth, or swelling
- Pain or tenderness
- Pus, drainage, or yellow crusts
- Blisters, sores, boils, or tender bumps
- Fever or swollen lymph nodes
Infection Versus Other Skin Rashes
Fungal, viral, allergic, and inflammatory conditions can resemble bacterial disease, including skin yeast infections that cause redness, itching, or irritation. Athlete’s foot is a fungal infection, while herpes is a viral skin infection, so antibiotics do not treat either condition.
Eczema, insect bites, contact dermatitis, or a pimple under the skin may also cause redness, swelling, or tenderness without a bacterial infection.
Signs the Infection Is Spreading
Expanding redness, worsening pain, fever, chills, red streaks, or new drainage may indicate spread. Symptoms can progress faster in a person with diabetes, poor circulation, or a weakened immune system. Severe pain that exceeds the visible skin changes requires prompt medical evaluation.
What Are Five Common Skin Infections?
The main types of bacterial skin disease differ in depth, appearance, and treatment needs. The phrase “skin diseases bacteria can cause” includes both surface infections and deeper soft-tissue infections. Bacterial skin infections include the following common conditions.
Cellulitis
Cellulitis affects deeper skin and tissue beneath it. It often causes a warm, painful, swollen area with borders that are difficult to define. Staphylococcus and Streptococcus species are frequent causes.
Impetigo
Impetigo usually causes red sores, blisters, or thick yellow-brown crusts. It often affects children and may appear around the face, arms, or legs. Direct contact with sores or contaminated items can spread it.
Folliculitis
Folliculitis is inflammation or infection around hair follicles. It often appears as small red bumps or pustules that resemble pimples. Friction, shaving, moisture, and bacteria may contribute, and the right folliculitis treatments depend on the cause and severity.
When folliculitis affects the scalp, a dermatologist-recommended shampoo may help address excess oil, buildup, yeast, or bacteria, depending on the underlying cause.
Boils and Skin Abscesses
A boil is a painful infection that begins around a follicle and forms a pocket of pus. Several connected boils may form a carbuncle. A larger abscess may require drainage rather than antibiotics alone.
Erysipelas
Erysipelas is a superficial form of cellulitis with raised, sharply defined borders. The skin may look bright red and feel painful or hot. Streptococcal bacteria commonly cause it.
MRSA and Antibiotic Resistance
Methicillin-resistant Staphylococcus aureus MRSA is a strain of staph bacteria that resists several common antibiotics. It can cause boils, abscesses, cellulitis, and other infections, but colonization does not mean active disease. A culture may help guide treatment when resistance is a concern.
Causes and Risk Factors
Bacteria often enter through breaks in the skin caused by cuts, scratches, bites, burns, shaving, or chronic skin disease.
Skin-to-skin contact and shared towels, razors, sports equipment, or clothing may spread some organisms. Moisture and friction can weaken the skin barrier and support bacterial growth.
Risk can increase with diabetes, poor circulation, swelling, chronic wounds, or immunosuppression. Close-contact sports, crowded living spaces, and poor wound coverage may also increase exposure.
Bacterial Infection on the Face
A bacterial infection on the face may involve impetigo, folliculitis, an infected wound, or cellulitis. Redness near the eyes may require closer assessment, as infection can involve the surrounding tissues.
Facial swelling, eye pain, vision changes, or trouble moving the eye should not be managed only through photographs.
Are Bacterial Skin Infections Contagious?
Contagiousness depends on the condition and whether open sores or drainage are present. Impetigo and some staph infections can spread through skin-to-skin contact or contaminated personal items. Cellulitis itself usually does not spread casually, although bacteria from an open wound may pass to another person.
Keep draining wounds clean and covered. Avoid sharing towels, razors, clothing, or athletic gear, and wash your hands after touching a bandage. Follow medical advice about work, school, sports, or close-contact activities.
How Doctors Diagnose Skin Infections
A clinician usually begins with a physical examination and a review of medical history. Different types of skin infections can look similar, so the appearance, location, depth, drainage, pain, and rate of spread help narrow the diagnosis. A culture of pus or fluid may identify the bacteria and help select an antibiotic.
Other tests may be needed when fungal disease, a viral infection, or another rash is possible. Blood testing or imaging may be appropriate for severe or deep infections. Remote review can provide initial context, but it cannot replace every physical examination, culture, or procedure.
How Are Bacterial Skin Infections Treated?
Treatment depends on the type, depth, location, and severity of the infection. Limited impetigo may respond to prescribed topical antibiotics, while cellulitis may require an oral antibiotic.
Severe infection, systemic symptoms, or high-risk medical conditions may require hospital assessment and intravenous medicine.
Abscesses often need professional drainage. Do not squeeze, cut, or drain a suspected abscess at home because this can spread infection or injure nearby tissue. Use antibiotics exactly as prescribed, and do not use leftover medication or share it with another person.
Can Treatment Happen Remotely?
Clear photographs and a detailed history may help a clinician assess visible symptoms and decide on next steps. Remote checks have limits when an infection is deep, spreads fast, or causes severe pain.
They also have limits when it is near the eye or linked to a fever. Cultures, drainage, blood tests, and direct examination require in-person care.
How Long Can a Skin Infection Last?
A bacterial skin infection may last from several days to several weeks, depending on its type, depth, severity, and treatment. Impetigo often improves within a few days and may clear in about 7 to 10 days with treatment, while cellulitis commonly requires about 7 to 10 days of antibiotics.
Deeper abscesses, recurrent infections, or infections linked to resistant bacteria may take two weeks or longer to resolve.
Some redness, swelling, or tenderness may persist as the skin heals, even after the infection starts to improve. Contact a clinician if symptoms worsen, redness continues to spread, a fever develops, or there is no clear improvement within 48 to 72 hours after treatment begins.
Slow healing may be due to an abscess requiring drainage, antibiotic resistance, poor circulation, immunosuppression, or an incorrect diagnosis.
When to Seek Urgent Care
Some symptoms may signal a deeper or rapidly progressing infection. Seek urgent medical assessment for:
- Fever with spreading redness or swelling
- Severe or rapidly increasing pain
- Purple, gray, blistered, or numb skin
- Redness or swelling near the eye
- Confusion, weakness, or trouble breathing
- Rapid progression in someone with diabetes or immune suppression
How to Prevent Skin Infections
Wash cuts and scrapes with clean water, then cover them with a clean dressing. Keep your hands clean, avoid sharing personal items, and wash clothing or towels that come into contact with drainage. Shower after close-contact sports and keep shared equipment clean.
Treat eczema, fungal infections, and other conditions that damage the skin barrier. Follow instructions for prescribed antibiotics and complete the directed course unless the prescriber changes the plan. These steps reduce transmission and help limit antibiotic resistance.
