Gluten is a composite of proteins, not a starch. The gluten is stored with starch in the endosperm of grass type grains, i.e. wheat, barley & rye. The gluten protein here is made up of something called gliadin and something called glutenin.
There are also stored proteins in the endosperm of rice and maize (corn), sometimes referred to as gluten, but the difference is that it lacks the gliadin.
It is the gliadin in the gluten, so to speak, that you react to. (Almost sounds like a song...can just see Gene Kelly dancing.)
Starch and gluten are two different things. Gluten is what helps to provides the framework in the cell structure of food when you are cooking or baking. It helps to make things expand in volume and hold it's shape. It helps things hold together. We have to use vegetable gums and things like Expandex to mimic that action. Potatoes and corn have starch too, and they, along with rice, are perfectly safe to eat unless you have an allergy to the food itself. Rice should be safe to eat; if you are worried about it, then just buy a brand that says it is gluten free and packed in a gluten free facility. I just usually buy off the shelf, and to date I have been lucky. I buy a lot of my rice and rice flours in the Asian section of one of my grocery stores, and I have not had any problems with them.