ABSTRACT. This study aimed to describe the first report of an outbreak of primary photosensitization in dairy goats caused by Froelichia humboldtiana. The disease occurred from March to May 2014, in a mixed flock of 15 Saanen, Alpine, and crossbred lactating goats. The entire flock was affected; however, the Saanen and cross-bred goats developed more severe lesions, and their milk production decreased by as much as 75%. Lesions were progressive and consisted of skin hyperemia, edema, and necrosis, especially in depigmented areas. An experimental study with two goats resulted in photodermatitis, similar to that observed in the natural cases, 10?14 days after the beginning of plant ingestion. Serum activities of aspartate aminotransferase (AST) and -glutamyltransferase (GGT) and, direct, indirect, and total bilirubin serum concentrations were within the normal ranges. In conclusion, F. humboldtiana causes primary photosensitization in goats with a negative impact on milk production. © 2016 Elsevier Ltd. All rights reserved.