Excessive Shedding

Our sweet girl (5 years old) has been struggling with shedding for the past years after she became fully grown. She is currently on an allergy shot because she would itch. She doesn’t itch at all anymore but shes still shedding so so much. We’ve gone to multiple vets and theres not much help. Is this normal? It happens on a normal shedding cycle but its around 2 months of shedding until she starts growing it back. Does this happen for other Shibas?

She lives in a pretty drastic climate - 40c summer and -40c winters

Shes on: purina pro senstive skin lamb and oat Ultra oil Salmon treats Cytopoint