Oxacillin is a semi-synthetic isoxazolyl penicillin antibiotic used mainly to treat staphylococcal mastitis in dairy cattle. Because mastitis directly affects milk safety and quality, effective treatment protects both animal welfare and the milk supply. Milk from treated cows is generally considered safe for human consumption five days after the final treatment, provided the withdrawal period is observed. In dairy food safety, antibiotic residue monitoring verifies compliance with maximum limits, preventing allergic reactions in sensitive consumers and avoiding disruption of cheese and yogurt fermentation. Proper veterinary use of oxacillin thus supports udder health while safeguarding the dairy processing chain.