just been to see friends litter and i found a flea what can she use??

Frontline spray on, prescription only though, so she'll have to get it from her vet.

Frontline spray will be fine for 5 week old pups.Unfortunately you can only buy the spray from the vets so your friend will probably have to ring them and explain so she doesn't have to take pups to vets and risk exposing them to infection.Please do not use the spot-on,it must be the spray.Good luck.