I think that there's the possibility of some confusion here. What type of parasites are you referring to? If its those on your dog's skin, such as fleas and ticks, Credelio has quite a few fans here. (It's a tiny tablet, available only on prescription, that's easy to hide in food).
However if it's intestinal parasites that you're referring to, you'll clearly need something different. Once again though, given your dog's sensitivity to anything on her skin, it might be best to ask your vet for something that's easy to hide in her food.
I've spent many hours trying to get 'spot on' treatments applied to my cats, simply because I didn't fancy the idea of getting tablets into them. However, now that I've worked out which tablets I can hide in their food, life has got a lot easier both for me and for them. Perhaps the same might be true as far as Tora is concerned?