Dozens of owners said their dogs were suffering with vomiting and diarrhoea earlier this month after visiting the Yorkshire coast and one veterinary practice in Whitby said it was "inundated" with cases.
But public health experts from councils in the area claim there is no direct link to the beach and canines that have not visited the coast have fallen ill with similar symptoms.
Cases have been reported across the country and a number of vets in Yorkshire say the dogs are suffering with gastroenteritis after contracting a virus.
In a statement, Swanzdale Veterinary Care Centre in Scarborough, said: "We have seen several dogs who have not been anywhere near the beach or the sea becoming affected.
"For now we would advise avoiding heavily dog-walked areas (which includes the local beaches) and stopping your dog having close contact with other dogs, and not letting them drink out of communal water bowls."
Cheryl Holdsworth, from The Friendly Animal Clinic in Sowerby Bridge, wrote: "From cases we've seen, it is highly contagious from the speed with which it has moved through the canine population throughout the country.
"It started approximately 10 days ago and is still affecting many dogs. Avoid walking /exercising your dog whilst they are poorly. It can start as either vomiting or diarrhoea.
"We are advising clients to phone us for advice. Most dogs are needing treatment.
"Some dogs have had to be hospitalised. It is affecting different dogs to varying severity."
The British Veterinary Association said it will not speculate on the cause of the illness, but owners should remain vigilant.
President Justine Shotton said: "We are aware of a spike in cases of dogs falling ill from gastroenteritis-like symptoms in several parts of Yorkshire and the North East.
"At this time, we can't speculate on what might be at play in this situation, and there is currently no evidence to suggest a direct link between the illness and the dogs visiting the beaches.
"While pet owners are understandably worried, the cases may be part of a normal increase in gastroenteritis that vets see during the colder months. Our advice to owners is to contact their local vet for prompt treatment if their dog show signs of possible illness, such as vomiting and diarrhoea."
The University of Liverpool's Small Animal Veterinary Surveillance Network said it "could be caused by a range of infectious and non-infectious agents including parvovirus and canine enteric coronavirus".
It also said data shows gastrointestinal disease in dogs is more prevalent during the winter months.
The Department for Environment, Food & Rural Affairs said it is aware of these cases and owners should contact a vet if their dog becomes ill.