Serum levels of heavy metals in childhood eczema and skin diseases: friends or foes

Abstract

The incidence of eczema has been increasing in developed countries. Environmental and hygiene factors have been incriminated. Although air and food pollution with heavy metals have been considered as possible culprits, these factors have never been investigated in Hong Kong. To evaluate if quality of life and eczema severity are associated with abnormal serum levels of six common heavy metals, namely, cadmium, lead, mercury, selenium, copper and zinc. Serum or whole blood was taken for measurement of six heavy metals from patients referred to the pediatric dermatology clinic. Eczema severity (SCORAD and NESS) and quality of life (CDLQI) were recorded. A total of 110 patients with eczema and 41 patients with miscellaneous skin conditions were recruited. Serum levels of the six heavy metals were generally within the upper limits of local reference ranges. Zinc levels were below the lower reference limit of 9.4 mum in 66 patients with eczema (60%) and 22 non-eczema patients (53%). Forty-four patients with eczema (40%) and 24 (58%) in non-eczema group had low copper levels. In eczema patients, lead levels were generally within normal limits but their levels were positively correlated with poor quality of life (CDLQI: r = 0.22 and p < 0.05), disease severity (objective SCORAD: r = 0.33 and p < 0.005; NESS: 0.20, p < 0.05), eosinophil count and log-transformed IgE. Copper/zinc ratio also correlated with NESS and CDLQI and was generally higher than non-eczema skin diseases. Our findings help reassure parents that levels of heavy metals generally do not exceed the local reference ranges for toxicity. However, lead levels have significant correlations with disease severity, quality of life and atopy. Low zinc and copper levels are commonly found in pediatric skin diseases and their significance needs to be determined.