THE "FLARE-UP PHENOMENON": NEW ONSET OF DISTANT DERMATITIS DURING PATCH TESTING

Abstract

<h3>Introduction</h3> Allergic contact dermatitis is common, affecting ∼20% of adults, and is often evaluated via diagnostic patch testing.[1] In rare cases, patch testing may result in worsening of pre-existing dermatitis, but development of de novo lesions is unusual.[2] <h3>Case Description</h3> In 2018, a 46-year-old woman experienced severe, bilateral eyelid swelling with intense itching and skin cracking, along with an eczematous rash on her chest and hands. Inpatient workup revealed no infectious/rheumatologic cause, and patient was diagnosed with contact dermatitis from an unknown trigger. After a period of remission, in 2021 patient again developed bilateral eyelid rash without involvement of the hands or chest. Following treatment with topical steroids, eyelid rash resolved. Epicutaneous patch testing was performed (T.R.U.E. TEST). 36h after patch test placement, patient experienced, rapid intensification of eczematous lesions around the eyelids, as well as new onset of rash on the dorsa of her hands, which had been unaffected prior to patch testing (Figure 1). 72h read was positive to colophony and fragrance mix (+1). Systemic and topical corticosteroids were prescribed for presumed flare-up phenomenon, with subsequent resolution of periorbital and hand rash. <h3>Discussion</h3> While generally well-tolerated, diagnostic patch testing has been associated with the "flare-up" phenomenon, worsening pre-existing eczema—and, in this case, leading to the development of de novo lesions.[3] Flare-up is more common in polysensitized patients, as was seen in our case.[2] The mechanism of the "flare-up phenomenon" is poorly understood, but is believed to involve reactivation of memory T cells at previous sites of disease.[3]