The most useful thing you can do when your dog starts reacting on a walk is to stop worrying about what anyone else thinks, because the moment your attention shifts to the stranger watching you, your choices start being driven by embarrassment and impulse rather than by what your dog actually needs from you in that moment. That is far easier said than done, and almost every owner of a reactive dog feels judged when it happens, but most of those feelings are not true, and the more you can keep your focus on you and your dog, the clearer your thinking will be.
Staying polite and light-hearted helps everyone, so a cheerful “good morning, sorry” as you move away keeps the other person on side, and a breezy explanation such as “come on, it’s only a man in a hat” tells them your dog is worried rather than dangerous, which usually earns you compassion instead of a glare. Your emotions do not cause your dog’s reactivity, although dogs are certainly tuned in to how we feel, so choosing calm and cheerful over cross and frustrated will only ever make the situation easier, and that applies even when someone else’s off lead dog has caused the whole thing, because shouting at them changes nothing and simply adds more tension to a moment that already has plenty.
Space is always your friend, so as soon as a reaction starts, try to put as much distance as you can between your dog and whatever has worried them, using your body language, a little gentle lead pressure and a cheerful “this way” to guide them off rather than dragging them. If your dog tends to freeze or lie flat rather than bark and lunge, moving them is much harder, and that is when you may need to advocate for them by politely asking the other person to give you a wide berth. It also helps to keep the lead loose, because people naturally tighten everything when they feel worried, and a dog who is feeling scared and suddenly finds the lead short and tight may decide that escape is no longer an option and that fighting is the only choice left.
Calling your dog’s name or using their recall in the middle of a reaction rarely works, because a dog in that state genuinely cannot process what you are saying, and every ignored recall chips away at a cue you want to stay reliable. Silly noises such as a kissy sound tend to work far better, because they are not an instruction but they spark curiosity, and curiosity is often enough to break that intense focus for a second so you can move away.
Once you are out of the situation, the recovery matters just as much, so give your dog time to sniff, shake off and settle before they meet anything else, and keep walks in busy places short so that reactions are not stacked one on top of another with no downtime in between. Over time, scanning ahead and creating space before your dog tips over the edge keeps them in a thinking state where real learning can happen, because the goal is never a dog who has no emotions but one who reacts less often, less intensely and recovers more quickly each time.