Are there any common ingredients in robitussin (guaifenesin) and neosporin that i could be allergic to?

Neosporin more like: Robitussin (guaifenesin) has various formulations, often with guiafenesin, which is pretty well tolerated. Rare to truly see an allergy. However, neosporin ointment can certainly cause allergic contact dermatitis on the skin or mucous membranes, either from the antibiotic itself, or an excipient in the preparation. However, are you referring to hives (urticaria)? Then I'd see allergist or dermatologist.