With no child allergy specialist service in Wellington, four-year-old Fletcher Ng's parents had no choice but to take him to a private specialist in Auckland.

The family now faces the prospect of paying almost $500 every six months for blood tests to monitor his food allergies - a galling thought when the tests are free elsewhere.

His mother, Cushla Thomson, said severe eczema made Fletcher's early life miserable.

"He was practically covered in this scaly, itchy rash and clawed at his skin all the time."

Fletcher was given skin prick tests, but two of his major food allergies - dairy and wheat - were missed. Doctors prescribed steroids and directed that he should be wrapped in wet bandages for 24 hours a day.

"Basically we were told we would just have to put up with it."

In desperation, the family flew to Auckland a year ago for a private consultation.

Blood tests showed Fletcher was allergic to dairy, wheat, soy, egg, potatoes, nuts and fish. He has to be retested every six months.

Since Capital and Coast and Hutt Valley district health boards stopped subsidising laboratory tests ordered by private specialists 18 months ago, patients have been hit with hefty bills. Ms Thomson said some "cooperative" GPs would order tests on behalf of specialists, though the practice was forbidden by health boards.

Allergy New Zealand chief executive Penny Jorgensen said many families were forced to seek private treatment for their children because of the lack of specialist allergy services.

There are only three child allergy specialists in New Zealand - all of them in Auckland - and only one works in the public sector. "To make them pay for lab tests on top of that is going to be too much for some families and ultimately it's going to force people back into the overloaded public system," Ms Jorgensen said. She called for a public debate to be led by the Health Ministry.