Eosinophilic cellulitis

Overview

Eosinophilic cellulitis, also known as Wells syndrome, is a rare inflammatory skin condition characterized by sudden-onset, red, swollen, and often itchy or painful skin lesions that resemble infectious cellulitis. Despite its name, eosinophilic cellulitis is not caused by infection and does not respond to antibiotics. It is distinguished by the presence of eosinophils—a type of white blood cell involved in allergic reactions and immune responses—in the affected skin. The condition is benign but can be recurrent and may cause cosmetic and physical discomfort.

Causes

The exact cause of eosinophilic cellulitis is unknown, but it is thought to be triggered by immune dysregulation. Potential triggers and associations include:

• Insect bites or stings

• Vaccinations or injections

• Drug reactions (e.g., penicillins, NSAIDs)

• Infections (e.g., fungal, bacterial, or parasitic)

• Systemic diseases such as leukemia, lymphoma, or autoimmune conditions

• Idiopathic cases: In many instances, no clear trigger is identified

Wells syndrome is considered an eosinophilic dermatosis, meaning the inflammation is primarily driven by eosinophils in the skin tissue.

Symptoms

Symptoms of eosinophilic cellulitis may appear suddenly and vary in presentation, but typically include:

• Red, swollen skin plaques: Often warm and tender, mimicking bacterial cellulitis

• Itching, burning, or pain

• Blisters or vesicles: May appear on top of the inflamed areas

• Hyperpigmentation: Darkening of the skin at affected sites during healing

• Recurrent flare-ups: Lesions may reappear in the same or different locations

• Lesions usually occur on limbs but may appear anywhere on the body

Unlike infectious cellulitis, eosinophilic cellulitis is not associated with fever or systemic symptoms in most cases.

Diagnosis

Diagnosis is based on clinical examination, laboratory findings, and histopathology. Key diagnostic steps include:

• Skin biopsy: Essential for diagnosis; shows eosinophilic infiltration and "flame figures" (eosinophil granule deposits on collagen fibers)

• Complete blood count (CBC): May reveal peripheral eosinophilia (elevated eosinophils)

• Rule out infection: Culture tests and lack of response to antibiotics help distinguish from bacterial cellulitis

• Allergy or drug exposure history: May provide clues to potential triggers

Accurate diagnosis is important to avoid unnecessary antibiotic treatment and to guide appropriate therapy.

Treatment

Treatment of eosinophilic cellulitis focuses on reducing inflammation and relieving symptoms. Common management approaches include:

• Topical corticosteroids: For mild or localized cases

• Systemic corticosteroids: Such as prednisone for widespread or severe inflammation; often leads to rapid improvement

• Antihistamines: To reduce itching and allergic response

• Immunosuppressive agents: In recurrent or steroid-resistant cases (e.g., dapsone, cyclosporine, or azathioprine)

• Avoidance of known triggers: If a specific medication or allergen is identified

Most patients respond well to corticosteroids, but relapses are common and may require long-term management.

Prognosis

Eosinophilic cellulitis is a benign condition with no known risk of progression to systemic disease. The prognosis is generally favorable, but recurrence is common, especially in individuals with underlying triggers. Chronic or recurrent cases may lead to cosmetic concerns or persistent skin discoloration. With appropriate treatment and trigger avoidance, most patients can manage the condition effectively and experience symptom-free periods.