Chronic Forehead Rash: Diagnosis and Management
A 1cm rash on the forehead persisting for 4 years most likely represents a localized chronic dermatitis requiring skin biopsy for definitive diagnosis, with initial empiric treatment using emollients and mild topical corticosteroids while ruling out secondary infection and contact allergens.
Diagnostic Approach
The chronic 4-year duration makes this unlikely to be atopic eczema alone, as atopic dermatitis typically presents with a more variable, relapsing-remitting course rather than a single persistent plaque 1. However, several key differential diagnoses must be considered:
Primary Differential Diagnoses
- Localized chronic eczema/dermatitis - Most common cause of a persistent facial plaque, particularly if there is personal or family history of atopy 2, 3
- Contact dermatitis - Consider exposure to cosmetics, hair products, sunscreens, or topical medications that may contact the forehead 2, 3
- Seborrheic dermatitis - Common on forehead and scalp, though typically more diffuse
- Psoriasis - Can present as isolated plaques, though less common on forehead
- Tinea faciei - Fungal infection should be excluded, especially with chronic unresponsive lesions
Critical Red Flags Requiring Urgent Evaluation
- Multiple uniform "punched-out" erosions or vesiculopustular eruptions suggest eczema herpeticum, a medical emergency requiring immediate systemic acyclovir 2, 4
- Crusting, weeping, or honey-colored discharge indicates secondary bacterial infection requiring bacterial culture and antibiotics 1, 2
- Failure to improve after 1-2 weeks of appropriate treatment warrants dermatology referral 2, 3
Essential History and Examination
Document these specific factors 1:
- Aggravating factors: exposure to soaps, cosmetics, hair products, sunscreens, or topical medications 2, 3
- Pruritus severity and impact on sleep
- Personal or family history of asthma, hay fever, or atopic disease 1
- Previous treatments attempted and their effectiveness
- Presence of similar lesions elsewhere on the body
Physical examination must assess 1:
- Exact size, borders, and morphology of the lesion
- Presence of scaling, crusting, weeping, or vesiculation
- Evidence of excoriation from scratching
- Look for similar lesions in other locations, particularly flexural areas
Initial Management Strategy
First-Line Treatment
Apply emollients liberally and frequently, at least twice daily and after washing, to restore the skin barrier 2, 3. Use moisturizers with high lipid content 2.
Hydrocortisone 1% (mild potency) applied 3-4 times daily is the appropriate first-line topical corticosteroid for facial involvement 2, 3. The face requires particular caution with corticosteroid potency to avoid skin atrophy 1.
Trigger Avoidance
- Replace regular soap with gentle, soap-free cleansers as soaps remove natural lipids from already compromised skin 1, 3
- Avoid washing with very hot or very cold water 1, 3
- Discontinue all cosmetics, hair products, and topical medications applied to the forehead to rule out contact dermatitis 2, 3
When to Add Antibiotics
If crusting or weeping is present, send bacterial swabs and initiate flucloxacillin for presumed Staphylococcus aureus superinfection 1, 4. Deterioration in previously stable lesions often indicates secondary bacterial infection 1.
Diagnostic Testing
Skin biopsy is essential for a 4-year persistent lesion that has not been definitively diagnosed 1. While atopic eczema is typically diagnosed clinically, a single persistent plaque of this duration warrants histopathological confirmation to exclude other diagnoses 1.
Consider patch testing if the pattern suggests allergic contact dermatitis or if the lesion is recalcitrant to standard treatment 3.
Fungal culture or KOH preparation should be performed if tinea faciei is suspected.
Follow-Up and Escalation
Reassess in 1-2 weeks 2, 3. If no improvement with initial therapy:
- Refer to dermatology for definitive diagnosis, consideration of skin biopsy, and potential escalation of treatment 2, 3
- Consider stronger topical corticosteroids (though use cautiously on face), topical calcineurin inhibitors, or phototherapy for recalcitrant cases 1, 3
Common Pitfalls to Avoid
- Do not use potent or very potent topical corticosteroids on the face without dermatology guidance, as this can cause skin atrophy, telangiectasia, and perioral dermatitis 1
- Do not prescribe oral antihistamines for pruritus - they are ineffective for reducing itch in eczema and may cause sedation 2, 5
- Do not delay skin biopsy for a 4-year persistent lesion - chronic single plaques require histopathological diagnosis 1
- Do not assume this is simple atopic dermatitis without meeting diagnostic criteria, which include itchy skin condition plus three or more additional features including typical distribution patterns 1