What could be causing small itchy patches at the base of the skull underneath the hair?

Small Itchy Patches at the Base of the Skull Under Hair

The most likely diagnosis is tinea capitis (scalp ringworm), and you should obtain scalp scrapings or hair pluckings for fungal culture to confirm the diagnosis before initiating systemic antifungal therapy. 1

Most Common Causes to Consider

The differential diagnosis for small itchy patches at the base of the skull includes:

• Tinea capitis - fungal infection of scalp hair follicles and surrounding skin, most commonly caused by Trichophyton or Microsporum species 1
• Seborrheic dermatitis - inflammatory condition with scaling and pruritus, particularly common in areas with high sebum production like the scalp 2, 3
• Contact dermatitis - allergic or irritant reaction to hair products, dyes, or styling implements 4
• Folliculitis - inflammation of hair follicles from bacterial, fungal, or non-infectious causes 5
• Psoriasis - can present as localized patches with scaling and itching 2, 3

Diagnostic Approach

Obtain specimens for laboratory confirmation before treatment:

• For suspected tinea capitis: Pluck affected hairs or use a blunt scalpel to collect hair and scalp scale; scalp brushings with a cytobrush improve sensitivity 1
• Specimens should be collected in paper or card packs for fungal culture 1
• Multiple sampling methods (scraping plus brush) increase diagnostic yield 1

Clinical examination should specifically assess:

• Pattern and distribution of lesions (localized patches vs. diffuse) 4
• Presence of scaling, pustules, or crusting 1
• Hair loss or broken hairs ("black dots") 1
• Signs of inflammation or boggy masses (kerion) 1
• Examine the entire body skin, not just the scalp 4

Treatment Strategy

If tinea capitis is confirmed or highly suspected:

• Systemic antifungal therapy is required - topical treatments alone are insufficient 1
• Laboratory confirmation guides appropriate antifungal selection 1
• Post-treatment samples should confirm clearance 1

For symptomatic relief while awaiting culture results:

• Topical hydrocortisone can temporarily relieve itching associated with minor skin irritations, inflammation, and rashes 6
• Avoid using topical corticosteroids long-term without definitive diagnosis, as they can worsen fungal infections 1

Critical Pitfalls to Avoid

• Do not treat empirically without obtaining specimens - the causative organism determines appropriate systemic therapy 1
• Do not rely solely on clinical appearance - many scalp conditions present similarly with scaling, inflammation, and pruritus 3
• Do not mistake kerion for bacterial abscess - this inflammatory variant of tinea capitis requires antifungal, not just antibiotic therapy, though secondary bacterial infection should not be overlooked 1
• Do not use topical antifungals alone for tinea capitis - systemic therapy is necessary due to follicular involvement 1

When to Consider Alternative Diagnoses

• If fungal cultures are negative: Consider seborrheic dermatitis, contact dermatitis, or folliculitis 2, 4
• If symptoms are chronic and refractory: Evaluate for systemic causes of pruritus including hepatic, renal, thyroid, or endocrine disorders 7
• If no visible lesions are present: Consider neuropathic or psychogenic causes, though this requires exclusion of dermatologic and systemic etiologies first 7, 4