I admin a group on Facebook for owners of reactive dogs and the one thing that comes up over and over is why the group does doesn’t allow warning gear to be suggested. In fact, the rescue doesn’t allow it either. Now I understand that it seems like a good idea to put on a harness or collar or leash that says “Do Not Pet” or “Nervous”, but there are actually more downsides than upsides to that kind of gear.
First, many of the collars/harnesses/leashes/vests are VERY bright colours. As a result, they CAN attract children due to the bright colours. This is not a great thing if your dog is reactive.
Secondly, many folks actually come closer to you and your dog to read what the gear says and often want to stand around and talk to you about why your dog wears a harness that basically says “Stay away from me”.
I had several warning harnesses donated and I tested them out on my very stable, solid non-reactive pug just to see what folks did. And sure enough, between the hot pink colour and the writing, folks did not give us distance or space, they came right over which is the opposite of what you would want if you are going to put this on your dog.
The last reason this equipment is not such a hot idea has to do with liability. As an example, a number (in fact, most) of insurance companies won’t insure you or will threaten to cancel your insurance if you have a “Beware of Dog” sign on your house. You CAN have “Guard Dogs on Duty” or “Dogs on Premises” but you can’t have a sign that implies your dog is dangerous.
The same applies to dog equipment that essentially implies the dog may react aggressively to certain human directed interactions. You can certainly have “In Training”, “Do Not Feed”, “Blind”, or “Deaf”, but gear that implies the dog may cause harm can get your insurance cancelled on your double quick. The rescue’s insurance company was very clear that they would not cover us if we had dogs that wore warnings.
The notable exception to this is a muzzle. A muzzle does actually prevent injury even if the human acts like a dope. And dogs may wear muzzles for many reasons that have nothing to do with behaviour issues.
As I said above, I understand why folks think this is a good idea, but it’s really not. If you are worried about your dog’s behaviour issues creating problems for other humans, then muzzle training is the way to go.