Delayed hypersensitivity to palladium dichloride: 15‐year retrospective study in a skin allergy unit

Abstract

Background Metal allergies are the most frequent causes of allergic contact dermatitis. Although the use of palladium is increasing, it is not included in any baseline series. Objective To assess the prevalence of hypersensitivity to palladium and to describe the clinical and demographic characteristics of patients who are sensitized to palladium dichloride (PdCl2). Methods A single‐centre, retrospective study of 15 years of patch testing with the Spanish baseline series supplemented with PdCl2 2% pet. was performed. We collected clinical and demographic data and data on co‐sensitization among the metals studied, and we compared patients who were sensitized to palladium, with or without co‐sensitization to nickel, with the rest of the study population. Results Among the 3678 included patients, 730 (19.9%) were sensitized to nickel sulfate. The prevalence of sensitization to PdCl2 (n = 316, 8.6%) was higher than the prevalence of sensitization to potassium dichromate (n = 240, 6.5%) and similar to the prevalence of sensitization to cobalt chloride (n = 353, 9.6%). Only 26 (8.2%) of the patients sensitized to palladium were not co‐sensitized to nickel. The percentage of men and patients aged ≥40 years was higher in this subgroup than in the patients with nickel co‐sensitization. Conclusions Given the high prevalence of hypersensitivity to PdCl2, this metal salt should be included in the Spanish baseline series, notwithstanding the frequency of co‐sensitization to nickel.

Contact Allergy—Emerging Allergens and Public Health Impact

“…In consecutively (routinely) patch-tested Spanish patients (n = 3678), palladium dichloride 2% pet. caused 8.6% positive reactions; only 26/316 positive patients were not also sensitised to nickel [46], confirming observations made elsewhere [47]. Patch test reactions to vanadium (tested as trichloride 1% pet.)…”

Immunological Mechanisms of Metal Allergies and the Nickel-Specific TCR-pMHC Interface

“…Depending on the study, between 2.3 and 72% of Ni-allergic patients also react to Co 2+ with a positive patch test reaction [82,242,243]. Between 11 and 40% of Ni-reactive individuals respond to Pd 2+ [87,242,243]. In several studies, up to 83% co-sensitization of Co-allergic patients to Ni 2+ is also observed in combination with other metals [244,245].…”

“…Additionally, Pd is present in jewelry and industrial catalysts in the car industry because of its resistance to corrosion [2]. Although the use of Pd is increasing, it is not included in any standard test baseline series [87]. Out of 910 ACD patients in the USA, 12.1% tested positive for Pd.…”

“…PdCl 2 is the most frequent (3%) allergen of the "dental metal series" detected in dental technicians with occupational ACD [89]. The incidence of Pd allergies has frequently been explained through cross-reactivity since isolated allergy to Pd is rare [87]. Currently there is no EU legislation to limit the amount of Pd in consumer products.…”

Kontaktallergien – Neu aufkommende Allergene und Auswirkungen für das Gesundheitswesen

“…Bei konsekutiv (routinemäßig) epikutan getesteten spanischen Patienten (n = 3.678) rief Palladiumdichlorid 2 % pet. bei 8,6 % positive Reaktionen hervor, und nur 26 dieser 316 positiven Patienten waren nicht zugleich auch gegen Nickel sensibilisiert [46], was andernorts gemachte Beobachtungen bestätigt [47]. Epikutantestreaktionen auf Vanadium (getestet als Trichlorid 1 % pet.)…”