Peruano

Its nice to talk about pepper spray or halt, but cost, availability, and grief from dog owner can be a problem. I frequently deal with aggressive dogs that need to be trained to not chase bikes.
I use a weak solution of ammonia water (usually used to wash windows) - dilute it to 25% or less - 10% works and carry it in a Vietnamese Hot Sauce bottle - the one with the narrow spout that twists to open. It will never be confused with your water bottle - is small enough to go in a jersey pocket - sprays a direct jet but in small enough quantities that you don't use your entire reserve on the first shot and the dogs recoil as soon as they get a whiff of the ammonia or feel it on their nose or eyes. It does not harm the dog but it sure gets his attention. Yes some will say that ammonia might burn the eyes but not in the dilute solution and under the circumstances the dog is not likely to get much more than a few drops unless you hold him down and dowse him with it. A couple of shots on separate days and the dogs on my regular route do not chase my bike or my ankles. The ammonia solution is available in any hardware or grocery store and should be as available internationally as in the USA. Works for me and I think I could justify my choice with the angry dog owner who happened to see me repel his dog. tom