my cat has acquired fleas over the last month and is climbing the walls scratching and shaking her ears. i brought some of the Bob Martin flea spray and am trying to treat it as it is impossible to get her to take tablets or hide them in food (believe me, i have tried). My question is how often is it safe to use the spray ? I assumed it was once a week but I think it needs more than that... help, any cat lovers out there .. my poor cat is so miserable