Kim Kardashian -- Is That a Hickey ... or Psoriasis?

On the same day she revealed she's publicly dating Kanye West, Kim Kardashian was sporting a suspicious red blotch on the side of her neck.

At first we thought -- hickey, for sure -- but then we remembered Kim suffers from psoriasis ... a condition that can cause itchy dry red patches on the skin.

We reached out to Kim for comment so she could settle the debate once and for all ... but we haven't heard back.

The debate rages on ...