I have a bite of some kind on my left shoulder. it is not raised but does itch. i have had it for a few days. it feels like the redness is starting to spread towards the middle of my chest. should i be worried or go see a doctor?

Increasing redness:: After a bite, a little redness is normal, but if begins to spread over the next few days and does not get better with an allergy pill, it may mean that the bite has gotten infected, which may need treatment with antibiotics. So yes, get checked and see, if it keeps getting worse, becomes painful, or you run a temp.

I would. : If, as you say, redness is spreading, then you need to be concerned about an infection. I would seek attention at an urgent care in expectation of receiving an antibiotic.

Yes see a doctor: if the redness is spreading from you shoulder to your chest, then yes see your doctor, it still could be a simple allergic reaction, but we have to make sure that you do not have some kind of cellulitis,spreading, and you might need to have oral,systemic antibiotic, so please see your doctor.