Shedding a light on the importance of photopatch testing: A 12-year experience in a dermatology unit.

BACKGROUND: Photopatch testing has been standardized for diagnosing photoallergic contact dermatitis but is still infrequently used. OBJECTIVES: To characterize photopatch test (PPT) results and their clinical relevance. METHODS: We collected retrospective data from patients photopatch tested in our Dermatology Unit (2010-2021), using the European PPT 'baseline' series, other allergens, and patient's own products, when appropriate. RESULTS: Out of 223 patients, 75 patients (33.6%) were reactive with 124 positive PPT reactions, considered relevant in 56/223 patients (25.1%) and in 72/124 reactions (58.1%). Most reactions were caused by topical drugs (n = 33; 45.8%), such as ketoprofen or promethazine, and 7 (9.8%) by systemic drugs, such as hydrochlorothiazide and fenofibrate. 'Classical' ultraviolet filters were responsible for six positive PPT reactions whereas there was only three relevant PPT to the 'newer' UV filters. Patients' sunscreens/cosmetics or plant extracts caused 10 positive PPT each. Additional patch test reactions were observed, mostly to Tinosorb® M. CONCLUSION: Contrary to the trend in ACD, most positive PPT reactions were caused by topical drugs, outweighing ultraviolet filters and cosmetics. We stress the low reactivity to the 'newer' UV filters included in the PPT series. PPT was occasionally positive in systemic drug photosensitivity, but overall PPT reactivity was low.

A closer look at allergic contact dermatitis caused by topical ophthalmic medications.

BACKGROUND: Allergic contact dermatitis caused by topical ophthalmic medications (OftACD) is frequently difficult to confirm with patch testing and, therefore, it is considered uncommon. METHODS: We collected retrospective data from a cohort of 65 patients with suspected OftACD patch tested in our Dermatology Unit (2005-2021) according to ESCD guidelines, using a series of topical drugs and excipients (Chemotechnique Diagnostics), including betaxolol and timolol 5% pet. kindly supplied by the pharmaceutical industry. Also, frequently used ophthalmic medications as well as patient's own products were also patch tested 'as is' in most patients. RESULTS: Positive patch tests to ophthalmic medications occurred in 44 patients (67.7%) (38F/6M; mean age 63.1 years), with 102 positive reactions. Most positive reactions were associated with active ingredients (n = 56), especially aminoglycoside antibiotics (n = 27), followed by excipients (n = 24) such as sodium metabisulfite (n = 7). There were also positive reactions to topical products tested 'as is' (n = 22), mostly containing beta-blockers, but only five of these reacted to the active ingredient. DISCUSSION: This study reinforces previous findings in OftACD, such as older age of onset, and the importance of antibiotics, contrasting with the progressively lower prevalence of excipients. In addition, it helps raising awareness for the sensitization to beta-blockers, which is probably underestimated. Patch test preparations for the diagnosis of OftACD may require protocol optimization.