Cercarial dermatitis (also named Swimmer's itch or Clam-digger's disease) was first described about 80 years ago, but today its impact is increasing and it is considered an emerging disease. This represents a hypersensitive or allergic reaction to Trichobilharzia spp, clinically characterized by initial erythema and cutaneous itching, followed by macular or papular eruptions, itching and occasionally diffuse erythema or urticaria. We report two cases of patients affected by a cercarial dermatitis after bathing in Lake Vico (Central Italy). We highlight these cases for the rarity of this dermatitis and its increasing prevalence, also in previously non-affected geographical areas, associated to a high level of social discomfort.