Why does it take 6 months for catch up loss to occur?
Everything happens slowly in hair as it only grows at a rate of 1/2 inch per month. Much of the hair loss or reversal of it from drugs like Propecia (starting or stopping it) occurs in the 6 month time frame to be detectable. Usually, when you stop the drug and the drug was working well, the loss will occur in the first 3 months.