I'm thinking definitely a bite of some sort. The excessive reaction may simply be because your ear has skin, cartilage, blood vessels and not much else, so anytime I've been bitten by a mosquito on my ear, it is always terribly itchy and red. The more I scratch, the more it gets red, hot and itchier. Having said that, it may indeed be something more than a simple spider bite, flea, bedbug or mosquito. All spiders are poisonous because they produce venom. But there are only some that can cause harm to humans. If it is a poisonous spider (i.e. brown recluse or black widow, the two poisonous ones we have around here that can actually do harm to humans) you need to see a doc pronto. Since you wrote this Thursday and it is now Friday, I'm guessing you already know if it is getting worse or not. Better safe than sorry, so get to a doc if you haven't already. Post later and tell us how this goes, I'm curious what is is!