In general, the welts caused by flea bites are found more on the lower part of the body like the legs and ankles. It can also bite in the waist area, armpits, and other fold of body joints such as knees and elbows. When the fleas come in direct contact with your skin from the pet's body, the skin bumps can be noticed in the areas like forearms and elbows where you were holding the pet.