Since I have had adverse reactions to certain antibiotics (tetracycline, ampicillin), is it safe for me to use chlorhexidine mouthwash for gum pain?
You had reactions to tetracycline and ampicillin, which are antibiotics, but chlorhexidine mouthwash is not an antibiotic; it is an antiseptic used locally for gum problems. It is generally safe for people with antibiotic allergies, though it may cause temporary taste changes, mild burning, or staining of teeth; true allergy is very rare. You can usually use it safely for gum pain, but if you develop swelling, rash, or breathing difficulty, stop and seek medical help.