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Concerning heavy metals in childhood eczema

We thank Pigatto and colleagues for kindly clarifying the important point that the serum levels of some heavy metals do not accurately reflect the chronic environmental exposure to toxic heavy metals. We apologize for the confusion that mercury and lead levels were indeed measured in whole blood, which was mentioned in the RESULTS but not in the METHODS of our publication. The mechanism of chronic environmental exposure of these metals is complex and is beyond the scope of this study. We also agree that the measurement of cadmium exposure caused by environmental contamination is high cadmium excretion in urine. This is reflected by the findings that no significant correlations between the serum levels and clinical scores are evidenced. The lack of any association also implies that the measurement of serum level of cadmium is not clinically useful. Food atopy and environmental pollution with heavy metals have been implicated as possible associated factors in childhood eczema. Seafood avoidance, with the exception of fish, is widely practiced among the Cantonese Chinese in Hong Kong. Fish is believed to be good for children and commonly consumed in the local diets. They might be a source of zinc, mercury, arsenic or manganese intake. These metals have been found to be associated with eczema and skin diseases. In subsequent research, we also evaluated whether fish atopy is associated with fish consumption, eczema severity, and levels of the four selected heavy metals. We found no difference in average weekly fish consumption and levels of the four heavy metals between eczema and noneczema groups. Serum levels of the four heavy metals were generally within the upper limits of local reference ranges in patients all these patients. In eczema patients, serum arsenic and whole-blood mercury levels correlated with days of seawater fish consumption per week (arsenic: p = 0.38, p = 0.001; mercury: 0.26, p < 0.005). No such difference was observed with freshwater fish consumption. Nevertheless, there was no difference between fish atopy (as evidenced by positive skin prick test) and non-fish atopy groups in terms of eczema severity, quality of life, and heavy metal levels. Fish atopy was present in approximately 25% of patients with eczema. Although days of seawater fish consumption per week was correlated with serum arsenic and whole-blood mercury levels, these metals generally did not exceed local normal reference ranges. In the quest for associations between heavy metals and childhood eczema, it appears that whole-blood lead level appears to be the only measurement that we investigated that has positive correlation with disease severity, quality of life, and atopy.