Big red spots that sting and itch, also spread quickly. What. Are they.?

Hives without bees. Unless you know what you are allergic to, it is often very difficult to find the specific cause your rash--likely hives. This can be quite itchy and may have burning sensation to it. They often come rather quickly, spread, and often subside in few hours; but could last for days. Benadryl/zyrtec/claritin and/or calamide lotion may help. If worsens, consult doc. Good luck.