President Donald Trump appeared to have a large red rash on the back of his neck Monday. While speaking at the White House about his illegal war with Iran, Trump was spotted with a dark red patch of skin peeking out from under his collar. In a photograph taken by AFP photographer Saul Loeb, a large scab is visible.It wasn’t immediately clear what caused the red mark. Possible causes of a red rash could include contact or atopic dermatitis—also known as eczema—psoriasis, or heat rash. It could al...