Plunge dipping of sheep in organophosphate or synthetic pyrethroid solutions controls ectoparasites including sheep scab, but the dipping process itself causes stress and carries drowning and chemical exposure risks.
Sheep dipping involves a genuine welfare trade-off: the stress and risk of the dipping process must be weighed against the welfare harm of untreated ectoparasitic disease. Sheep scab causes intense, relentless pruritus — affected animals rub against fences, bite their fleeces, and develop progressively larger areas of inflamed, wool-free skin. The condition is profoundly distressing and continues to worsen without treatment. Plunge dipping, when conducted correctly, is rapidly effective across the whole fleece at a fraction of the cost of injectable alternatives for large flocks. The welfare risks of dipping — drowning, inhalation, hypothermia from wet fleece in cold weather — are manageable with proper technique: appropriate bath length, staffing, weather timing, and post-dip facilities. The operator safety requirements for organophosphate dips are demanding, and many farmers have switched to pyrethroid dips that carry lower human health risk. Maintaining flock biosecurity to prevent scab introduction is the most welfare-effective approach — preventing disease eliminates both the disease suffering and the treatment stress.