a trick to check for fleas shown to me by my vet,
comb the dogs hair well then bang the comb on a hard surface.... get a paper towel and damp it with water then wipe the surface where you banged the comb if the paper towel had red specks on it the dog will have fleas. The red is ofcourse blood.. from flea poo and scabs from itching and being bitten.
If you wish to go to the vets thats fine but
[email protected] sell the same stuff alot cheaper than my vets...

you will need to know the dogs body weight though.