Can internal swelling, redness, and heat in my left forearm be an allergic reaction to cipro?

Could be a reaction: Medications can cause all types of rash. It might also due to other causes like infection on that area Check with your doctor please

Possible: Since Cipro has been known to induce tendinitis , it is possible that this is the side effect you are experiencing. However this is a known side effect and not an allergic one. Must stop Cipro immediately and avoid doing anything strenuous for at least a month if this is from Cipro to avoid potentially tendon rupture.