Imported models have a sort of shell?

I have imported a model from blender into unity. It looks fine until I went back into Blender and added an armature to the model. Now the model seems to have a shell around the outside.

As you can see there is a faded looking shell (I guess you could call it that) on the outside of my model. Thankyou in advance.

This is done in 3ds max, but it addressses the issue of smoothing, if that’s what you are after: