Kerion: Symptoms, Types, Causes and Treatment

Kerion is a dramatic and often alarming inflammatory reaction of the scalp (or occasionally other hairy areas) triggered by a fungal infection. While it may look like a severe bacterial abscess, kerion is actually a hypersensitivity response to dermatophyte fungi and requires prompt, accurate diagnosis and targeted therapy. Understanding its symptoms, different forms, underlying causes, and best treatments is crucial for preventing scarring and permanent hair loss, especially in children. This article provides a comprehensive overview, synthesizing the latest research to help patients, caregivers, and healthcare professionals recognize, understand, and manage kerion effectively.

Symptoms of Kerion

When kerion develops, its symptoms are usually hard to miss. Unlike the subtle and silent onset of most fungal scalp infections, kerion presents as a swollen, tender, and often pus-filled mass. These symptoms can be mistaken for a bacterial abscess or cellulitis, which may lead to inappropriate treatments like antibiotics or even surgical drainage that won't resolve the problem.

Appearance	Sensation	Associated Signs	Source(s)
Boggy mass	Tenderness	Purulent discharge	1 2 6 11
Erythema	Pain	Regional lymphadenopathy	1 2 4
Alopecia	Itchiness	Black dots, crusting	1 2 6

Table 1: Key Symptoms of Kerion

Classic Clinical Features

Kerion typically manifests as a tender, erythematous (red), boggy swelling on the scalp or, less commonly, on other hairy areas like the beard or limbs. The mass can range from a few centimeters to large patches, and is often studded with pustules or oozing pus. Unlike other scalp infections, the affected hair often falls out easily, leading to dramatic, circumscribed hairless patches (alopecia) 1 2 6.

Associated Signs

• Purulent Drainage: The lesion may ooze pus, which contributes to its mistaken identity as a bacterial abscess 1 2.
• Black Dots: Broken hairs, appearing as black dots, are a common finding within the bald area 1.
• Crusting and Matting: Thick crusts and matted hair are often seen, especially in young children 2.
• Regional Lymphadenopathy: Swelling of nearby lymph nodes, particularly in the neck, is frequently noted 1 2 4.
• Other Symptoms: While pain and tenderness are almost always present, some individuals might experience itching or burning sensations.

Systemic Symptoms

Fever and general malaise are rare, as kerion is primarily a localized immune response rather than a systemic infection 1 2.

Types of Kerion

While the term "kerion" often refers to a particular manifestation of tinea capitis, there are several recognized types and presentations, depending on the causative fungus, affected area, and individual immune response.

Type/Location	Common Pathogens	Population Affected	Source(s)
Scalp Kerion	T. mentagrophytes, M. canis, T. tonsurans	Children, esp. prepubertal	1 2 3 5 6 11
Kerion Celsi	T. tonsurans, M. canis	Children	5 8 10
Beard/Body Kerion	Zoophilic dermatophytes	Men (beard), adults	6
Neonatal Kerion	T. mentagrophytes	Neonates (rare)	2

Table 2: Types of Kerion

Scalp Kerion

The scalp is by far the most common site for kerion, particularly among prepubertal children. Scalp kerion often results from infection with zoophilic dermatophytes (those originating from animals), such as Microsporum canis or Trichophyton mentagrophytes 1 3 6 11. However, in urban settings, infections by anthropophilic species (human-associated), especially Trichophyton tonsurans, are increasingly common 1 5 10.

Kerion Celsi

Kerion celsi is a classic term for severe, boggy, inflammatory tinea capitis. It can be caused by several dermatophyte species and is sometimes used interchangeably with "scalp kerion" in clinical practice 5 8 10.

Kerion in Unusual Sites

• Beard (Tinea Barbae): In adult men, kerion may appear in the bearded region, caused by similar fungi 6.
• Other Hairy Areas: Though rare, kerion can also develop on the arms, wrists, or thighs, displaying the same boggy, inflamed characteristics 6.

Neonatal Kerion

Kerion in newborns is extremely rare but possible. Cases have been reported in infants as young as a few weeks old, often due to T. mentagrophytes 2.

Causes of Kerion

Kerion is not the result of a typical infection, but rather an exaggerated immune response to certain fungi. Understanding the causes helps in both diagnosis and prevention.

Causative Agent	Source/Reservoir	Transmission Mode	Source(s)
Zoophilic fungi	Animals (cats, rabbits, dogs)	Direct/indirect contact	1 3 6 11
Anthropophilic fungi	Humans	Person-to-person	1 5 10
Environmental	Contaminated objects	Fomites	3 11

Table 3: Causes of Kerion

The Role of Dermatophytes

Kerion is caused by dermatophytes—fungi that infect hair, skin, and nails. The most common species implicated include:

• Trichophyton mentagrophytes
• Trichophyton tonsurans
• Microsporum canis
• Trichophyton verrucosum
• Less commonly, Trichophyton violaceum, Microsporum audouinii, Trichophyton rubrum, and others 1 4 5 6 7.

Animal (Zoophilic) Sources

Many kerion cases are traced to contact with infected animals—especially cats, dogs, and rabbits. These animals may show bald patches or subtle skin changes. Family outbreaks can occur when a household pet is the source, or in environments with high animal density (such as farms) 1 3 6 11.

Human (Anthropophilic) Sources

In urban areas, person-to-person transmission is becoming more frequent, especially in crowded living conditions or among children sharing combs, hats, or bedding. Asymptomatic carriers can maintain the cycle of infection 1 5 10 11.

Environmental Reservoirs and Fomites

Dermatophyte spores can persist for weeks on objects like hairbrushes, pillows, bedding, and clothing. Poor hygiene and shared personal items facilitate spread within households and schools 3 11.

Pathogenesis: Immune Response

Kerion develops not just from the presence of fungus, but from a robust T-cell mediated hypersensitivity reaction to the invading dermatophyte. This immune response is what causes the intense inflammation and tissue destruction seen in kerion, rather than direct fungal invasion 1 2.

Treatment of Kerion

Effective treatment of kerion hinges on accurate diagnosis, eradication of the fungus, and prevention of complications like scarring alopecia. Prompt therapy is crucial to minimize permanent hair loss.

Approach	Medication/Action	Key Point	Source(s)
Systemic antifungals	Griseofulvin, Terbinafine	Mainstay of treatment	1 2 5 6 8 9 10 11
Topical therapy	Ketoconazole (adjunct only)	Not effective alone	1 11
Corticosteroids	Prednisolone (oral/intralesional)	No added benefit proven	8 9 10
New therapies	ALA-PDT (photodynamic)	Emerging option	12

Table 4: Treatment Approaches

Systemic Antifungal Therapy

• Griseofulvin: Traditionally the first-line therapy, especially for Microsporum infections. Doses are adjusted for weight and continued for 8–12 weeks 1 2 5 6 8 9 10 11.
• Terbinafine: More effective for Trichophyton species and preferred in many regions due to shorter course and better tolerability 1 11.
• Itraconazole/Fluconazole: Alternatives for refractory or severe cases 11 12.
• Duration: Treatment continues until clinical resolution and negative fungal cultures, typically 6–12 weeks.

Topical Therapy

Topical antifungals alone (like ketoconazole cream or shampoo) are insufficient for kerion, as they do not penetrate the hair follicle deeply enough to eradicate the fungal infection. They may, however, be used adjunctively to reduce surface contamination and transmission 1 11.

Corticosteroids

Although steroids (oral prednisolone or intralesional injections) have been proposed to decrease inflammation and minimize scarring, multiple randomized trials show no additional significant benefit in cure rates or time to recovery when combined with antifungals 8 9 10. Routine use is not recommended.

New and Emerging Therapies

• Photodynamic Therapy (ALA-PDT): In select, resistant cases, 5-aminolevulinic acid photodynamic therapy has shown promise, especially where standard antifungals have failed or are contraindicated 12.

Supportive Measures

• Screening Contacts: All household members and pets should be examined and, if positive, treated to prevent reinfection 1 3 11.
• Environmental Cleaning: Regular cleaning and disinfection of home and pet environments, laundering bedding and clothing, and replacing or disinfecting hair care tools are essential 3 11.
• Avoid Incision/Drainage: Kerion is often misdiagnosed as a bacterial abscess. Incision and drainage is not indicated and can worsen outcomes 1.

Preventing Complications

Early and appropriate treatment is essential to avoid scarring and permanent hair loss. Delays in therapy increase the risk of irreversible alopecia 1 4.

Conclusion

Kerion represents an intense immune reaction to a common fungal scalp infection, but its dramatic presentation can easily mislead even experienced clinicians. Understanding the nuances of its symptoms, types, causes, and treatments is vital for effective management.

Key points covered:

• Kerion typically presents as a boggy, tender mass with pus and significant hair loss, frequently misdiagnosed as a bacterial abscess.
• It is most common in children, but can affect adults and even neonates.
• Causes include both animal and human dermatophyte species, with transmission via direct contact or contaminated objects.
• Prompt treatment with systemic antifungals is critical; corticosteroids do not add benefit in most cases.
• Screening close contacts and environmental cleaning are vital to prevent recurrence.
• New therapies like photodynamic therapy may be useful in refractory cases.

Early recognition and appropriate therapy can prevent permanent hair loss and halt the spread of this highly contagious condition. If you or someone you know notices a dramatic, tender swelling on the scalp with hair loss, seek prompt medical attention—kerion is treatable, but time is of the essence.