Whats wrong with my dog?

She has red, irritated skin between her toes and the skin around her nails looks painful. She is an 8 month old Jack Russell x Shi Tzu. I heard that Shi Tzu's are prone to skin conditions? I'm not sure if it's true though. I have been appliying salty water onto her paws and the irritated skin. We will take her to the vet next week soometime. What is wrong with my dog?