What is the cause of a persistent rash in a patient taking Preservision (Omega-3 fatty acids) that has not responded to triamcinolone acetonide, ketoconazole (Nizoral) cream, clobetasol propionate, and nystatin, despite prior dermatologist evaluation?

Persistent Rash Unresponsive to Multiple Topical Therapies: Diagnostic Considerations and Management

The most likely diagnosis is a delayed hypersensitivity reaction to PreserVision (containing omega-3 fatty acids, vitamins, and minerals), and the patient should immediately discontinue this supplement while transitioning to systemic therapy with oral antihistamines and a short course of oral corticosteroids. 1, 2

Primary Diagnostic Consideration: Drug-Induced Eczematous Eruption

The temporal relationship between PreserVision initiation in August and rash onset strongly suggests a delayed hypersensitivity reaction or systemic contact dermatitis. 1, 2

• Eczematous drug eruptions can occur days to weeks after medication/supplement initiation and may not respond to topical therapies alone. 2
• The failure of multiple high-potency topical corticosteroids (clobetasol propionate, triamcinolone acetonide) and antifungals (ketoconazole, nystatin) indicates this is likely not a primary dermatologic condition but rather a systemic reaction. 1, 3
• Systemic contact dermatitis can present with persistent cutaneous symptoms despite topical avoidance measures when the allergen continues to be administered systemically. 1

Immediate Management Steps

1. Discontinue the Suspected Culprit

• Stop PreserVision immediately - this is the most critical intervention. 1, 2
• The supplement contains multiple potential allergens including zinc, copper, vitamins C and E, and omega-3 fatty acids, any of which could trigger delayed hypersensitivity. 1

2. Initiate Systemic Therapy

Since topical treatments have failed, systemic therapy is warranted:

• Start oral prednisone 0.5-1 mg/kg/day (typically 40-60 mg daily for an adult) for 7-14 days with a taper. 4
• Add a non-sedating oral antihistamine: cetirizine 10 mg daily or loratadine 10 mg daily for 24-hour coverage. 5, 4
• Avoid diphenhydramine for long-term use due to sedation concerns in elderly patients. 5

3. Supportive Topical Care

• Apply emollients liberally at least twice daily to all affected areas to restore skin barrier function. 6, 5, 2
• Use alcohol-free, hypoallergenic moisturizers to prevent further irritation. 6, 5
• Continue medium-potency topical corticosteroids (triamcinolone 0.1%) to body areas, but switch to hydrocortisone 1% for intertriginous areas (groin) to avoid skin atrophy. 5

Alternative Diagnostic Considerations

If the rash persists after discontinuing PreserVision and completing systemic therapy:

Secondary Infection

• The failure of multiple treatments raises concern for secondary bacterial infection (impetiginization). 6
• Staphylococcus aureus is the most common culprit. 6
• Obtain bacterial swabs from affected areas and consider empiric antibiotic coverage if signs of infection present (increased warmth, purulence, crusting). 6, 5

Systemic Contact Dermatitis to Topical Medications

• Paradoxically, the patient may have developed contact dermatitis to one of the topical treatments (nystatin, ketoconazole, or even the corticosteroid vehicles). 1
• Patch testing can diagnose systemic contact dermatitis to topical medications including corticosteroids, antimicrobials (nystatin), and NSAIDs. 1

Follow-Up and Monitoring

• Reassess in 2 weeks: If no improvement after discontinuing PreserVision and completing systemic therapy, refer back to dermatology for skin biopsy and patch testing. 5, 4
• Watch for signs of severe cutaneous adverse drug reactions (DRESS, SJS/TEN), though these are less likely given the chronic, stable nature of this rash. 6, 3
• Document the reaction as a drug allergy to prevent future exposure. 6

Critical Pitfalls to Avoid

• Do not continue PreserVision "to see if it helps" - the temporal association is too strong to ignore. 1, 2
• Avoid prolonged use of high-potency topical steroids in the groin - this can cause irreversible skin atrophy and striae. 5
• Do not use topical retinoids or acne medications - these will worsen xerosis and irritation in drug-induced eczematous eruptions. 6
• Recognize that topical therapy alone is insufficient for systemic contact dermatitis - the allergen must be removed and systemic treatment initiated. 1, 2

Long-Term Prevention

• If eye health supplementation is still desired, do not rechallenge with PreserVision or any formulation containing the same ingredients. 1
• Consider alternative eye health strategies (dietary modifications, individual vitamin supplementation with different formulations) only after complete resolution. 1
• Maintain regular emollient use even after resolution to prevent recurrence. 5, 4