While most owners want their dogs to enjoy their freedom in the park, it could be argued they shouldn't be taken off their lead until they've built up a strong recall.
However, many allow their dogs to roam around off-leash without knowing whether they'll come back to them when they call their name.
A vet is urging owners against shouting 'my dog is friendly' when it inevitably approaches a strange dog or person when venturing around off-lead.
Speaking to Reddit, he warns this could put their pet at risk of either being attack by another dog or being stolen by an opportunist.
The vet said: "You should never shout 'my dog is friendly' when your dog is off-lead in a public place because it puts them and others in danger.
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"Your dog might be friendly but there's no guarantee the other dog is. By allowing them to run up to a strange dog, you're entering them into a dangerous situation.
"They would have run up to them, spooked them, and could be attacked as a result. The reactive dog is responding in the only way it knows how."
Claiming to have seen many pets come in to his surgery after being attacked by another dog at the park, the vet is urging people to keep their dogs on lead in busy or unfamiliar places.
"It isn't fair on the other owner as they may be trying to train this behaviour out of their reactive dog," he added.
"Equally, a dog could be anxious, and having another dog run up to it could frighten it. Not every dog is confident or likes being approached."
As dog thefts reach a seven year high, the vet claims shouting 'my dog is friendly' makes them a target to thieves.
He added: "The other thing which could happen by shouting 'my dog is friendly' in a public place, especially a park, is you're leaving your dog open to being stolen.
"If your dog is off-lead and running towards strangers then somebody could easily leash them up and take them away from you. This is why we urge people to get their dogs microchipped - it is also the law.
"Opportunists could be waiting in parks for somebody to tell them how friendly your dog is. It makes them an easy target, especially if they're half a field away from you."
Wanting to help owners keep their pets safe when out and about, he is encouraging them to train a strong recall, keep them in sight at all time and put them on a long lead in busy or unfamiliar settings.
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