My contacts always get foggy when my allergies are really bad, but I’ve also noticed that they fog up when I put certain kinds of lotion or sunscreen on my face. I think it has something to do with your eyes getting irritated enough that they produce a little extra gunk (technical term, I know), but probably not enough that you’d notice it if you weren’t wearing the contacts.
When it’s allergies, there’s not much I can do for it except put saline drops in every now and then to clear up the fog. If you do use lotion or makeup of any kind on your face, you might want to try not using it for a day or two and see if that helps – you might just need to switch to a different brand…