Blowfly strike (flystrike) — caused primarily by Lucilia sericata larvae — represents one of the most severe welfare conditions in sheep, causing intense pain, tissue destruction, and death if untreated. UK surveys estimate 1–3% of sheep are struck annually. Prevention strategies include dagginess management (crutching), fly monitoring, chemical preventives (organophosphates, insect growth regulators), and genetic selection for breech wrinkle-free conformation. The phasing out of mulesing in favour of surgical-alternative preventives raises new welfare considerations around procedure pain. Early detection technologies using electronic nose, behavioural sensors, and image recognition are under development. Welfare-positive interventions include prompt treatment, pain relief at detection, and integrating strike risk into farm welfare plans.