Cellulitis: Symptoms, Types, Causes and Treatment

Cellulitis is a common and sometimes serious bacterial skin infection that affects millions of people worldwide each year. Despite its frequency, it can be tricky to recognize, as its symptoms may overlap with other conditions. Understanding cellulitis—its symptoms, types, causes, and available treatments—is crucial for prompt intervention and recovery. This article will guide you through all aspects of cellulitis, using evidence-based insights from recent clinical research.

Symptoms of Cellulitis

Cellulitis can develop quickly and may become severe if not treated. Recognizing the symptoms early is key to preventing complications and ensuring effective treatment. The infection typically affects the deep layers of the skin, and its symptoms are both local and systemic.

Symptom	Description	Common Location	Source(s)
Erythema	Redness of the skin	Legs, face	1 2 3 5
Swelling	Localized edema	Any body area	1 2 3 5
Warmth	Increased skin temperature	Affected region	1 2 3 4
Tenderness	Pain to touch	Affected region	1 2 3 4
Fever	Elevated body temperature	Systemic	5
Lymphadenopathy	Swollen lymph nodes	Regional	1
Ill-defined Borders	Blurred edge of redness	Affected area	1 3

Table 1: Key Symptoms of Cellulitis

Understanding the Symptoms

Cellulitis most often appears as a red, swollen area that feels hot and tender to touch. The redness typically has indistinct, blurred borders, unlike some other skin infections that have sharply demarcated edges 1 3. The most commonly affected sites are the lower legs and the face, but cellulitis can occur anywhere on the body 1 2 5.

Local Symptoms

• Redness (Erythema): The hallmark of cellulitis is a patch of skin that turns red due to inflammation and increased blood flow 1 2.
• Swelling and Warmth: The infected area swells and feels hotter than the surrounding skin, a result of the body's immune response 1 3.
• Tenderness or Pain: The area is usually painful, especially when pressed 1 2 3 4.

Systemic Symptoms

• Fever and Malaise: Some individuals develop fever, chills, or a general feeling of being unwell, indicating the infection may be spreading 5.
• Lymphadenopathy: Swelling of regional lymph nodes may occur as the body responds to the infection 1.

Atypical or Severe Presentations

In severe cases, symptoms can progress to involve systemic signs such as rapid heartbeat, confusion, or even signs of sepsis. Additionally, involvement of deeper tissues or the lymphatic system may be indicated by red streaks or rapidly spreading redness 1 2.

Types of Cellulitis

While cellulitis is broadly defined as a bacterial infection of the skin and subcutaneous tissues, it encompasses several types based on its cause, appearance, and depth of skin involvement. Distinguishing between these types is important for guiding treatment.

Type	Defining Features	Typical Cause	Source(s)
Typical (Classic)	Erythema, swelling, warmth, pain	Bacteria (Strep/Staph)	1 2 3 8
Erysipelas	Raised, well-demarcated edges	Streptococcus pyogenes	9
Eosinophilic Cellulitis (Wells syndrome)	Acute, itchy plaques, often recurrent	Idiopathic, hypersensitivity	6 9
Orbital Cellulitis	Affects tissues around the eye	Sinus infection, trauma	4
Mimics (Noninfectious)	Similar symptoms, different causes	Vascular, allergic, autoimmune	4 7 9

Table 2: Types of Cellulitis and Related Conditions

Exploring the Different Types

Typical (Classic) Cellulitis

This is the most common form, usually caused by bacteria such as Streptococcus or Staphylococcus aureus. It presents as diffuse redness, swelling, and pain in the affected area, often without a clear border 1 2 3 8.

Erysipelas

Erysipelas is a distinct but related infection that affects the upper dermis and lymphatics. It typically features raised, sharply defined edges and is often caused by Streptococcus pyogenes 9. The face and legs are common sites.

Eosinophilic Cellulitis (Wells Syndrome)

This rare type presents with acute, itchy, red plaques that may mimic infectious cellulitis but are caused by an abnormal immune reaction. Lesions tend to resolve without scarring but often recur. Histology shows eosinophilic infiltration, and it often responds to corticosteroids or, in some cases, targeted therapies like JAK inhibitors 6 9.

Orbital Cellulitis

This severe form affects the tissues surrounding the eye. It is often a complication of sinus infections or facial trauma and requires urgent medical attention due to the risk of vision loss or intracranial spread 4.

Cellulitis Mimics

Not all that appears to be cellulitis is actually an infection. Several noninfectious conditions—such as deep vein thrombosis, contact dermatitis, gout, or drug reactions—can mimic cellulitis symptoms and must be ruled out before starting antibiotics 4 7 9.

Causes of Cellulitis

Understanding the underlying causes of cellulitis helps prevent recurrences and guides appropriate therapy. Most cases are due to bacterial infection, but specific pathogens, risk factors, and noninfectious mimics should be considered.

Cause/Pathogen	Frequency	Risk Factors	Source(s)
Streptococcus species	Common	Skin breaks, edema	1 2 10
Staphylococcus aureus	Common	Trauma, IV drug use, MRSA exposure	1 2 8
Other bacteria	Less common	Immunosuppression	8 10
Eosinophilic (noninfectious)	Rare	Immune dysregulation	6 9
Noninfectious mimics	Variable	Vascular, allergic, rheumatic	7 9

Table 3: Causes and Pathogens in Cellulitis

Delving Into the Causes

Infectious Causes

• Streptococcus species: Multiple studies indicate that β-hemolytic streptococci are a leading cause of cellulitis, with group A, C, and G being detected frequently 1 2 10.
• Staphylococcus aureus: This bacterium, including both methicillin-sensitive and methicillin-resistant strains (MRSA), is also a common culprit, especially in cases involving skin breaks, trauma, or exposure to healthcare settings 1 2 8.
• Other bacteria: Occasionally, other pathogens, including gram-negative bacilli, may be implicated, particularly in immunosuppressed individuals 8 10.

Risk Factors for Infection

• Skin trauma: Cuts, abrasions, insect bites, and surgical wounds provide entry points for bacteria 1 2.
• Chronic edema: Swelling due to venous insufficiency or lymphedema increases susceptibility 1 2 3.
• Immunosuppression: Diabetes, chronic kidney or liver disease, and use of immunosuppressive medications raise the risk and complicate management 2.

Noninfectious Causes and Mimics

• Eosinophilic Cellulitis: This is an immune-mediated process, not an infection, and features recurrent erythematous plaques with eosinophil infiltration 6 9.
• Conditions that masquerade as cellulitis: These include deep vein thrombosis, contact dermatitis, allergic reactions, gout, and more. Detailed clinical evaluation and sometimes diagnostic testing are necessary to distinguish these from true cellulitis 7 9.

Treatment of Cellulitis

Effective management of cellulitis hinges on early diagnosis and appropriate therapy. Antibiotics are the mainstay, but the choice of agent, route, and duration may vary depending on severity, risk factors, and local resistance patterns.

Treatment	Indication/Use	Key Points	Source(s)
Oral antibiotics	Mild to moderate cellulitis	Dicloxacillin, cephalexin, macrolides	2 3 11 12
IV antibiotics	Severe cases, systemic symptoms	Flucloxacillin, cephalosporins	13 12
MRSA coverage	High-risk populations	Clindamycin, doxycycline, TMP-SMX	2 8 12
Corticosteroids	Severe inflammation, noninfectious mimics	Wells syndrome, Sweet syndrome	6 9
Supportive care	All cases	Elevation, analgesia, hydration	1 3

Table 4: Main Treatment Strategies for Cellulitis

Approaches to Treatment

Antibiotic Therapy

• First-line agents: For most uncomplicated cases, oral antibiotics such as dicloxacillin or cephalexin are effective 2 3. Macrolides may offer advantages in some scenarios 11.
• IV antibiotics: Reserved for severe infections, systemic illness, or failure of oral therapy. Flucloxacillin and cephalosporins are commonly used 13.
• MRSA considerations: In patients at risk for MRSA (e.g., athletes, IV drug users, prior MRSA exposure), coverage should include agents like clindamycin, doxycycline, or trimethoprim-sulfamethoxazole 2 8 12.

Duration of Therapy

• Short courses: Evidence suggests that 5 days of antibiotics is generally sufficient, provided there is clinical improvement 2 12.
• Longer courses: May be needed for severe infections, slow response, or immunosuppressed patients. Some studies suggest that shorter courses may lead to higher relapse rates in severe cases 13.

Non-Antibiotic Treatments

• Corticosteroids: Indicated in eosinophilic cellulitis (Wells syndrome), Sweet syndrome, or severe inflammation not due to infection 6 9.
• Supportive care: Elevation of the affected limb, pain control, and maintaining hydration are important adjuncts 1 3.

Special Considerations

• Address underlying factors: Managing chronic edema, treating fungal infections of the feet, and improving skin hygiene can reduce recurrence risk 2.
• Differentiating mimics: Not all red, swollen skin is cellulitis. Misdiagnosis can lead to unnecessary antibiotics and delayed correct treatment 4 7 9.

Conclusion

Cellulitis is a common but potentially serious skin infection that requires a keen clinical eye for proper diagnosis and management. Its symptoms can overlap with many other conditions, making accurate identification essential for effective treatment. Evidence-based therapy, focused on the most likely pathogens and tailored to individual risk factors, offers the best chance for a full recovery.

Key points covered in this article:

• Symptoms: Redness, swelling, warmth, tenderness, and sometimes fever are classic; always consider systemic signs.
• Types: Typical bacterial cellulitis, erysipelas, eosinophilic cellulitis, orbital cellulitis, and noninfectious mimics.
• Causes: Primarily Streptococcus and Staphylococcus species; risk factors include skin breaks, edema, and immunosuppression.
• Treatment: Oral antibiotics suffice for most; IV therapy for severe cases. MRSA coverage for at-risk groups. Noninfectious mimics may need corticosteroids or other targeted therapy.
• Prevention: Address predisposing factors to minimize the risk of recurrence.

Recognizing cellulitis and distinguishing it from its mimics can significantly improve outcomes and prevent complications. If you suspect cellulitis, early medical evaluation and intervention are always advised.