Small bald patch on hind leg of 9 month old labrador *****?

i have a 9 month old labrador ***** she hasn't went into heat yet we are waiting for that to happen,she has a wee bit of ache on her tummy around her area which cleared up after anti bio-tics but the vet told me she would due to go into heat this was 3 months ago when ui checked her there was a wee small bald patch on her hind leg there is no lumps or wee beasties i check with the flea comb and bathed her just in case! shes not irritated by it at all i don't want the hle of taken her to the vet again shes there almost every month she is shedding her summer coat and has a wee bit of dandruff lol any help or suggestions on what it could be would be brill !!