As my psoriasis areas are pretty much covered up, I've never had a rude comment or stare, but I can imagine the uneducated comments.
To be fair, for someone who doesn't know the nature of a condition, it becomes the focus of the interaction, just to somewhat ease the tension. "So, I guess typing is a challenge without that finger?", or, "So, are stop signs and grass the same color for you?" People deal with the awkwardness differently. Some are innocent enough, but others are just... I'll just say "jerks", here. "Smug".
It is hard to ignore the ignorant, ironically, but they're easy to baffle with, "Well, you know what Schrödinger said about egoism, amirite?", and walk away, just to mess with them.
Basically, it's not about me and my psoriasis, it's about them and their a) ignorance, and b) their willingness to understand.
You want to understand? Sure, I'll explain.
You wanna be a jerk? Sure, I'll mess with your head, because it obviously doesn't have much else to do.
For me, as a caring person, it's not easy to dismiss someone, but when the negativity and ignorance is overwhelmingly obvious, I turn my back and move on to the good things in my life.