Credence goods are defined as products whose quality is difficult to evaluate. While online reviews have found to be effective in driving sales of search and experience goods, little is known about its effectiveness on credence goods. Using data from a cosmetic surgery platform, we investigate the impact of a novel form of online reviews, i.e. diaries, on the sales of credence goods. We also examine how the effects are moderated by the risk of surgeries. We focus on two diary features: number of images and post duration. We find the number of images has a positive impact on sales and the effects are stronger for more risky surgeries. These findings shed some light on the online marketing of credence goods.