A Sydney naturopath will face court over the treatment plan she allegedly devised for a baby boy, who police say was malnourished and close to death when he was admitted to hospital.

The eight-month-old boy was suffering from eczema when his mother consulted the naturopath in April for advice about alternative health treatments for her son, police said.

Police will allege Marilyn Bodnar, 59, who is also a registered nurse and a midwife, advised the child's mother to stop all medical and dermatological treatments for the child.

The following month, on May 28, the baby boy was admitted to Westmead Hospital suffering from severe malnourishment and developmental issues.