Photocontact Dermatitis and Its Clinical Mimics: an Overview for the Allergist

Abstract

Photo-contact dermatitis (PCD) describes the adverse cutaneous reaction that occurs in some patients as a result of simultaneous exposure to a contactant and to light. PCD can be subdivided into photo-allergic and photo-irritant dermatitis depending on whether the contactant respectively invokes an allergic or irritant reaction. Photo-irritant reactions are commonly caused by plants, psoralens, and medications taken internally, whereas photo-allergic reactions are commonly caused by sunscreens and topical nonsteroidal anti-inflammatory medications. The work-up of photo-contact dermatitis includes a thorough history and physical exam augmented by patch and/or photopatch testing, as the cornerstone of treatment for PCD is identification and avoidance of the irritating or allergenic chemical. Photo-contact dermatitis has the potential to significantly impact quality of life, so an informed approach to diagnosis and management is critical. Clinical mimics of PCD include polymorphic light eruption, solar urticaria, actinic prurigo, hydroa vacciniforme, cutaneous porphyrias, and systemic disorders with photosensitivity such as lupus and dermatomyositis. Herein, we review the clinical presentation, differential diagnosis (including the clinical mimics mentioned above), pathogenic mechanisms, diagnostic testing, and therapeutic considerations for PCD.

Blistering Distal Dactylitis: A Narrative Review

“…Traumatic burns [4,15] History of trauma Rare on fingertips of children (can be mistaken for signs of child abuse) History Clinical diagnosis Not purulent, unless bacterial superinfection Chemical burns [4,15] History of exposition to chemicals Can be hard to discern History Clinical diagnosis Allergic contact [8,40,41] Prior exposition to allergens (nickel, poison ivy, dyes, preservatives…)…”

Mucosal Macrophage Polarization Role in the Immune Modulation

“…However, the proportion of M cells in the intestine is not high; thus, the ability of M cells to deliver antigens is limited [55]. PP is an indispensable immunotolerance-related tissue, particularly in mice [56].…”

Photopatch Testing

“…As in ACD, previous exposure to the chemical or a related molecule is needed for sensitization, and reaction develops within 24-28 h in subsequent exposures. Sometimes the diagnosis of PhACD is not so obvious as other clinical patterns can occur (lichenoid, erythema multiforme-like) and the time relation with sunlight exposure may be less evident [11]. Most reactions do not occur immediately after sun exposure, and some also involve nonexposed areas or may have an asymmetric or exquisite distribution (only one arm/forearm in car/truck drivers or exclusively the lower lip after using mouth washes containing photosensitizers) [12].…”