What would be the probable causes of hair loss in dogs?

There are many causes of hairloss in dogs. Allergies are a major cause flea allergies are very common cause of hair loss. If you have an older dog endocrine diseases, such as hypothyroid disease, and Cushing's disease are other major causes of hair loss. Also other infectious causes include ectoparasites such mange mites or fungal like ringworm. Sometimes it can be even related to inherited disorders in some dogs

What would be the probable causes of hair loss in dogs?

Natural shedding. In some breeds, it happens constantly.

What would be the probable causes of hair loss in dogs?

If it is in patches, you might look at mange or even just hot spot.

What would be the probable causes of hair loss in dogs?

Shedding could be caused by skin allergies. Look at your dog's skin in the area where he/she is loosing fur and see if it looks irritated as compared to other areas of skin. If this is the case or if the fur loss is substantial you will probably want to consult a vet. Of course some amount of hair loss/shedding is normal especially when the seasons change, but you are probably asking the question due to more than normal hair loss.