What Causes Brown Spots Tuning White In Scratching On Neck?

hi. ive noticed some brown spots appearing on my neck. when i scratch them they become white. it has spread around parts of my neck. ive loocked up what it could be and i have found something that sounds exactly like what i have. its called tinea versicolor. it is a fungus. i have found treatments such as lotromin and selsun blue but i am wondering if this is what i have. the spots deffinately look like like a fungus and my father told me it was something he used to get as a child when he lived in the tropics. this fungus is said to have been derived from the tropics. so im guessing it is it. can you suggest anything i should do, like any over the counter medications, and how to treat it. i dont want it spreading and i want the quickest way to get rid of it. i also have psoriasis so i would like to know if this has anything to do with it.