First, Ni allergy is much more common in patients with obesity compared to the general population [35], and it is even more widespread among obese patients with worse metabolic profiles [36]; moreover, obese patients sensitized to Ni have a significantly lower baseline insulin-like growth factor 1 (IGF-1) level and a blunted growth hormone (GH) dynamic response compared to nonallergic ones [36]. The gene discussed is IGF1; the disease is obesity due to melanocortin 4 receptor deficiency.