What is the difference between ingrown hair and folliculitis of the groin?

Distinguishing Ingrown Hair from Folliculitis in the Groin

Ingrown hairs and folliculitis are distinct conditions that differ primarily by depth of involvement: ingrown hairs (pseudofolliculitis) result from a foreign body inflammatory reaction to hair that has curved back and penetrated the skin, while folliculitis is a superficial bacterial infection where inflammation and pus remain limited to the epidermis of the hair follicle. 1, 2

Key Clinical Differences

Ingrown Hair (Pseudofolliculitis)

• Pathophysiology: Occurs when curved or curly hair re-enters the skin after shaving, creating a foreign body inflammatory reaction around the ingrown hair shaft 2, 3
• Clinical appearance: Presents as inflammatory papules and pustules at the point where hair penetrates the skin, often with visible hair loops or trapped hairs beneath the surface 2, 4
• Distribution: Most common in individuals with curly or wavy hair, particularly affecting areas that are shaved regularly 2, 3
• Causation: Directly related to shaving technique and hair characteristics, not primarily infectious 3

Folliculitis

• Pathophysiology: Superficial bacterial infection (usually Staphylococcus aureus) where inflammation and pus are present in the epidermis of the hair follicle 1, 5
• Clinical appearance: Manifests as 1mm-wide vesicles, pustules, or papulopustules with inflammation limited to the follicular opening 5
• Progression: Can extend deeper through the dermis into subcutaneous tissue to form furuncles (boils) if untreated, which differs from folliculitis by having suppuration that creates a small abscess 1
• Causation: Infectious process, often associated with inadequate hygiene, trauma to skin from shaving, or S. aureus colonization 1

Practical Clinical Distinction in the Groin

• Look for visible ingrown hairs: If you can identify curved hairs penetrating the skin or trapped beneath the surface, this indicates pseudofolliculitis rather than primary folliculitis 2, 3
• Assess shaving history: Recent shaving with inadequate lubrication strongly suggests ingrown hairs, particularly in patients with curly hair 1, 6
• Evaluate depth of involvement: Superficial pustules limited to the epidermis indicate folliculitis, while deeper inflammatory nodules suggest progression to furuncles 1
• Consider distribution pattern: Folliculitis typically presents as multiple small pustules in hair-bearing areas, while ingrown hairs may show grooved scarring patterns from chronic inflammation 2, 4

Management Implications

For Ingrown Hairs

• Primary intervention: Improve shaving technique with adequate lubrication and avoid close shaving 1, 6
• Avoid manipulation: Do not pick or manipulate affected areas, as this increases infection risk 6
• Adjunctive measures: Apply moist heat to promote drainage of small lesions 6

For Folliculitis

• Mild cases: Apply topical clindamycin 1% solution or gel twice daily for up to 12 weeks 6, 7
• Moderate-to-severe cases: Consider oral tetracyclines as first-line systemic therapy 6, 7
• Abscess formation: Perform incision and drainage if fluctuant collections develop, as this represents progression to furuncles requiring surgical intervention 1, 7

Critical Pitfalls to Avoid

• Do not use topical acne medications without supervision, as they may irritate and worsen both conditions through their drying effects 6
• Avoid prolonged topical steroid use, which can cause perioral dermatitis and skin atrophy 6, 7
• Do not attempt needle aspiration for any fluctuant lesions, as this is successful in only 25% of cases overall and less than 10% with MRSA infections 7
• Recognize that both conditions can coexist: Ingrown hairs can become secondarily infected with bacteria, creating a mixed picture that requires addressing both the mechanical cause (ingrown hair) and the infection (folliculitis) 2, 3