Serum levels of protein oxidation products in patients with nickel allergy.

Nickel sensitization can not only induce allergic contact dermatitis (ACD), but also can induce an overlapping disease referred to as "systemic nickel allergy syndrome" (SNAS), characterized by urticaria/angioedema and gastrointestinal symptoms correlated to the ingestion of nickel-containing foods. This study was designed to determine if oxidative stress occurs in patients with nickel allergy. Thirty-one female patients (mean age 31.26 + 13.04 years, range 16-64 years) with confirmed nickel CD underwent oral nickel challenge because of clinically suspected SNAS; serum concentrations of protein carbonyl groups (PCGs) and nitrosylated proteins (NPs; biomarkers of oxidative stress) were measured before and after oral nickel challenge as well as in healthy female controls. Twenty-three of these 31 patients were diagnosed with SNAS because they had a positive reaction to the oral nickel challenge, and 8 patients had no reaction and therefore were classified as patients with contact nickel allergy only. Although both nickel-allergic patients and controls presented similar serum levels of PCGs, NP values in nickel-allergic patients appeared higher than in controls and tended to decrease after the challenge; furthermore, serum levels of NPs in patients affected by SNAS were higher (although not significantly) than in patients with nickel ACD only. The involvement of specific biomarkers of oxidative stress such as NPs and the lack of involvement of other biomarkers such as PCGs may help to better understand the alteration of the redox homeostasis occurring in nickel ACD and particularly in SNAS.