Creatine supplement is the most popular nutritional supplement and has various metabolic functions and sports medicine applications. Creatine supplementation increases muscle mass and can decrease muscular inflammation. Some studies have also suggested a beneficial role of creatine supplementation on chronic pulmonary diseases such as COPD and cystic fibrosis. Among athletes, the prevalence of asthma is high, and many of these individuals may be taking creatine. However, the effects of creatine supplementation on chronic pulmonary diseases of allergic origin have not been investigated. In the present study, we analyzed the effects of creatine supplementation on a model of chronic allergic lung inflammation. Thirty-one Balb/c mice were divided in four groups: Control, Creatine (Cr), ovalbumin (OVA), and OVA+Cr. OVA and OVA+Cr groups were sensitized with i.p. injections of OVA on days 0, 14, 28 and 42. OVA challenge (OVA 1%) and Cr treatment (0.5g/kg/day) were initiated on day 21 until day 53. We determined the index of hyperresponsiveness, the serum levels of OVA-specific IgE and IgG₁, and the total and differential cell counts in BALF. We also quantified airway inflammation, and the airway density of IL-4+, IL-5+, IL-2+, IFN-gamma+ and IGF-1+ cells, collagen and elastic fibers, and airway smooth muscle thickness. Our results showed that creatine in OVA-sensitized mice increased hyperresponsiveness, eosinophilic inflammation, airway density of IL-4+, IL-5+ and IGF-1 inflammatory cells, airway collagen and elastin content, and smooth muscle thickness. The results show that creatine supplementation exacerbates the lung allergic response to OVA through a Th₂ pathway and increased IGF-1 expression.