Milk allergy is among the most common food-related allergies. Milk-based products are recognized as plant protection products (PPPs) in several countries as alternatives to synthetic pesticides. The potential health risk for allergic workers, as well as the general population, is yet to be assessed. An investigation was conducted in the Vaud Canton of Switzerland, where milk-based products are sprayed by helicopter over vineyards. Air lactose concentration was measured at 14 locations via 25 mm IOM Multidust samplers. Residual lactose concentration was measured on the surface of leaves over 7 days following spraying. Surface contamination downwind from the treated area was estimated through computer-based modeling using AgDRIFT® software. The average milk protein concentration inside and outside the vineyard was 0.47 and 0.16 µg/m3, respectively. Milk residues persisted on the leaf surface for an average of three days. Modelling results revealed an estimated order of magnitude of 0.1–0.5 µg/m3 in milk proteins within one hour after the treatment in the close vicinity of the treated area. Our results reveal that the potential exposure to milk proteins in and around helicopter-treated vineyards is not negligible and that prevention messages targeted to individuals with severe allergies should be considered.