Lead reactivity - lunging and barking at dogs or people on the lead - affects millions of dogs and causes significant stress for both the dog and their owner.
Reactive behaviour causes genuine distress to affected dogs: the arousal state experienced during a reactive episode involves elevated cortisol and stress hormones, regardless of whether the behaviour appears aggressive. Dogs that react frequently experience cumulative welfare harm from repeated stress responses. Treating reactivity humanely through behaviour modification addresses the underlying emotional state rather than suppressing behaviour through punishment. A veterinary pain assessment should be part of any reactivity assessment, as physical discomfort is a significant but overlooked trigger.