Eda, N, Shimizu, K, Suzuki, S, Tanabe, Y, Lee, E, and Akama, T. Altered secretory immunoglobulin A on skin surface after intensive exercise. J Strength Cond Res 27(9): 2581–2587, 2013—The aim of this study was to determine the effects of high-intensity endurance exercise on skin immunity by estimating secretory immunoglobulin A (SIgA) and staphylococci on skin surface. Seven healthy adult men (age, 22.3 ± 2.0 years) performed bicycle exercise at 75% HRmax for 60 minutes from 2030 to 2130 hours. Secretory immunoglobulin A was obtained from 1 ml extraction liquids stirred with the microtube homogenizer in the open end of a polypropylene tube for 60 seconds. Secretory immunoglobulin A concentrations were measured using enzyme-linked immunosorbent assay. Staphylococci were harvested by pressed agar-based media against skin surface. Skin surface samples were collected from the chest and the forearm on the first day at 2030 hours (before rest, A1), 2130 hours (after rest, A2), and 2230 hours (after showering, A3); the next morning at 0700 hours (A4); on the second day at 2030 hours (before exercise, B1), 2130 hours (after exercise, B2), and 2230 hours (after showering, B3); and the next morning at 0700 hours (B4). Secretory immunoglobulin A concentration on the forearm was significantly lower at B2 (p < 0.05) and B3 (p < 0.05) than that at B1 and that on the chest at B1 tended to be higher compared with B2 (p = 0.084) and B3 (p = 0.075). The number of staphylococci was significantly higher at B2 than that at B1 (p < 0.01) and B4 (p < 0.01) on the forearm. We conclude that high-intensity endurance exercise might depress immune function and enhance infectious risk on skin surface. Coaches should encourage their athletes to take a shower and change into clean clothes immediately after sports activities and athletes should maintain a clean skin surface to decrease the infectious risk on skin surface.