|Many female dogs who are nursing puppies will lose a large amount of hair. This is not abnormal. Such a dog is often said to be 'blowing her coat.' The technical term for the cause of this loss is 'telogen effluvium.'
To understand the condition, it is important to know that a dog's hair is not always growing, but the growth goes through various stages. There is a growth phase (anagen) and a resting stage (telogen). The hairs in telogen are more easily shed than those in anagen.
During pregnancy and other stresses, hairs may enter telogen prematurely, and do so in large numbers. Hormone changes in the bitch may also play a role in this change.
The large numbers of hairs in telogen are shed simultaneously, and results in this condition of 'blowing the coat' in which the hair may actually come out in clumps. These hairs in telogen are actually being 'pushed out' by the growing hairs underneath them. As the new hairs grow in large numbers, we may sometimes observe that the 'new coat' is darker, less dense, and has a different texture.
A dog who is blowing her coat will benefit from daily brushing, which will also decrease the amount of hair that tends to accumulate in the house, on furniture, etc. Also, be sure she is receiving proper nutrition for a nursing dog.