What signs indicate my german shepherd has dog flea?

My german shepherd's neck hasn't got any hair because he always scatch the neck areas. Does he has allergies or fleas?And by the way , how does the fleas look like

look on his belly, by his scrotum, on his inner thighs, pull the hair aside..............if u see bugs crawling, u got flees, if not give him an oatmeal bath and a half a bendryl then take him to the vet when u get a chance

If he has a bad flea infestation, you can usually see the fleas if you check the fur on his stomach. Another and more reliable way of checking is to brush him, fill your sink with water and dump the brushed off hair in there. If there are any flea droppings, they will dissolve in the water and you will see tiny specks of red, since flea droppings are basically composed of blood.If you don't see any signs of fleas, then you are probably dealing with allergies. German Shepherd Dogs are a breed with allergy issues, so if you are not doing it already, put him on diet for allergy dogs and take him to the vet to have him tested.EDIT: Fleas look like tiny black/brownish/reddish flat ovals. Usualy they will be a bit smaller than a "0" as you see it here (all depending on your computer settings, of course). If you look closely, you can see a tiny head at the tapered end and long-ish hindlegs for jumping at the round end. Fleas are fast! If you catch one, keep it squished between your fingers and dump it in some water with a bit of soap in it, don't let it foam (the soap will minimize the water tension so that the flea won't be able to sit on the surface of the water and maybe escape that way). Dump the flea in the slighly soapy water and take a closer look.