Photopatch testing in Singapore: A 10-year retrospective study.

Area of Science:

• Dermatology
• Allergology
• Photodermatology

Background:

• Photopatch testing is the gold standard for diagnosing photoallergic contact dermatitis (PACD).
• Understanding common photoallergens is crucial for effective diagnosis and management.
• Previous studies have identified key allergens, but trends may evolve over time.

Purpose of the Study:

• To identify common photoallergens diagnosed via photopatch testing.
• To compare current findings with previous data and other centers.
• To evaluate the utility of personal item testing in PACD diagnosis.

Main Methods:

• Retrospective review of 90 patients undergoing photopatch testing.
• Testing included standard sunscreen series, extended series, and patient-provided personal items.
• Data collected from 2012 to 2021 at a tertiary dermatological referral center.

Main Results:

• 18.9% of patients were diagnosed with PACD, 13.3% with allergic contact dermatitis (ACD), and 4.4% with photoaugmented ACD.
• Oxybenzone (9.5%) and mexenone (3.6%) were the most frequent photoallergens.
• Ketoprofen in personal items was associated with PACD in 75% of relevant cases.

Conclusions:

• Organic UV absorbers like oxybenzone and mexenone continue to be significant photoallergens.
• Personal item testing is valuable, particularly for identifying allergens like ketoprofen.
• The overall frequency of PACD has decreased, but individual allergen relevance remains consistent.