Four Cats whom I allow outside in my relatively safe environment. They catch those wretched Fleas which they transport into the House where they colonise. Bedding, Carpets, Sofas then you infested. These work alongside their Spray (I used three) and have now subscribed to avoid it ever happening again. Of course, it certainly makes our furry family members suffer in silence if allowed ! Don't allow it, get them frequently treated.