• N A Gray, T M Esterhuizen, N P Khumalo, and D J Stein.
• Division of Dermatology, Groote Schuur Hospital and Faculty of Health Sciences, University of Cape Town, South Africa; Department of Psychiatry and Mental Health, Groote Schuur Hospital and Faculty of Health Sciences, University of Cape Town, South Africa. nicolagrayemail@gmail.com.
• S. Afr. Med. J. 2020 Apr 29; 110 (5): 409-415.

BackgroundAtopic dermatitis (AD) is a common chronic inflammatory skin condition that disproportionately affects children and is associated with reduced quality of life. Zinc deficiency may contribute to the pathogenesis of AD because zinc plays a role in epidermal barrier integrity and the immune system. Systematic review evidence suggests that low zinc is associated with AD, but limitations of included studies support further investigation.ObjectivesTo investigate hair zinc concentrations in children with AD v. healthy controls in a low- to middle-income country setting.MethodsOne hundred and five children aged 1 - 12 yea-rs participated in a frequency-matched for age case-control study. The outcome variable, AD, was confirmed by a clinician and corroborated using the UK Working Party criteria. The primary predictor, long-term average zinc concentration, was determined by measuring hair zinc using inductively coupled mass spectrometry. Baseline demographic characteristics, anthropometry and measures of socioeconomic status were included in our logistic regression analysis. Subgroup analysis was performed where interaction terms suggested effect modification.ResultsUsing data from the overall sample, population median hair zinc was not significantly different between children with AD and healthy controls. However, subgroup analysis suggested a clinically and statistically significant difference in median zinc between children with AD (175.35 µg/g) and healthy controls (206.4 µg/g) in the older age group (5 - 12 years) (p=0.01). In this age group, multivariable logistic regression analysis also found significantly decreased hair zinc concentrations in AD (odds ratio 0.83; 95% confidence interval 0.66 - 0.96; p=0.046).ConclusionsThe inverse association between zinc status and AD in children aged 5 - 12 years in our setting is consistent with the international literature. The clinical importance of decreased zinc levels in AD is not yet known. Further investigation into relevant underlying mechanisms seems warranted given the global reach of AD, its effect on quality of life, and the low cost of potential zinc-based interventions.

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