Allergic to Nothing

Conversation between me and Elias a couple of weeks ago:
E- Mommy, what was I allergic to when I was a baby?
M- Well, you were allergic to milk.
E- So I couldn't drink milk?
M- Right, you drank soymilk. But you couldn't eat cheese either. So you couldn't eat pizza. But you outgrew it, and now you love pizza, huh?
E- MmmHmm. So what am I allergic to now?
M- Nothing.

Conversation that occurred in my car on the way home from school Monday:
M- Hey sweetie, how was your day at school?
E- Good. Did you bring me a snack?
M- No, I didn't bring you a snack today. You can have a snack as soon as we get home.
E (with Elena agreeing)- Can we stop at McDonald's for fries?
M- No. But we will have a snack at home. I promise.
E- You really didn't bring me anything?
M- Right. So tell me about your day. Did you have Spanish today?
E- You brought me nothing?
M- (silence. I am NOT responding to this. I can see we are headed in a bad direction.)
E- You brought me NOTHING? But I am allergic to NOTHING! And you brought me NOTHING!?!
M- (still silence)
E- (under his breath, realizing I am not going to respond) Now I am going to have a rash... (quiet sobs)