Your question doesn't make sense. Mitisis IS the process by which humans grow, thus increasing the number of cells in the body. Mitosis is a process that includes 4 phases. What exactly are you asking?
Whenever a new drug, device, or food, is developed for use in animals, It has to be approved by the FDA before it can be sold and marketed to the public.
Don't use the exact words, I copied it from an FDA website so change the wording first before you submit. Good luck Lol.
Answer:
because your body is fighting against the disease