Practical Techniques: Photopatch Testing

Photopatch testing (PPT) represents the gold standard diagnostic evaluation for photoallergic contact dermatitis (PACD), a type IV hypersensitivity reaction to an antigen that occurs in the presence of ultraviolet A radiation. The most common photoallergens in the United States are organic sunscreen filters, whereas topical NSAIDs predominate in Europe. PACD is not rare among photosensitive patients; however, PPT is underperformed in clinical practice due to several limiting factors. Herein, we provide practical approaches to PPT based on expert opinion, including straightforward recommendations on patient selection and testing procedure.