Minor injury units (MIU) are helping cut pressure on hospital emergency departments in Devon and Cornwall but demand is increasing in holiday time.
Some staff said they were concerned they were seeing more patients at MIUs in need of 999 level care.
In May, Cornwall's MIUs had to call 999 for 80 patients - the highest number of such referrals in the last 12 months.
MIU bosses said it was "inevitable" people might try to have MIUs deal with more complex cases.
Seriously ill patients
Some nurses said the pressure on services meant more patients were ending up in the wrong place.
Laura Inniss, lead nurse at the Bodmin MIU, said her team had been seeing more patients who were seriously ill and needed to be taken to an emergency department.
She said: "Recently I had an 18-month-old girl who had reduced levels of consciousness and couldn't get an ambulance.
"The 999 handlers sent her to us and we're left with [dealing with] a serious condition."
Staff added that up to 70% of the people they were currently treating were visitors to Cornwall.
Dr Tamsin Anderson, joint medical director for Cornwall's NHS Foundation Trust, which runs MIUs, said treating so many tourists was helping take pressure off the emergency department at the county's main hospital near Truro.
She said Cornwall was "fortunate" to have MIUs and ambulances would look to see which patients could be managed by them.
But she added: "Obviously, we can't provide all of the services that an emergency department provides.
"It's inevitable that people would expect to try and see if we can look after slightly sicker people.
"But, of course, sometimes we do need to transfer people across to that emergency expert care."