Hi Andy,
Given that an adequate topside trial of erythromycin results in no problematic side effects, a normal course of this drug should pose no risk for scuba.
It is important that the diver with influenza or a related disease have recovered completely before returning to scuba. The respiratory and congestive effects of such conditions have obvious implications for safe diving.
Divers taking this medication will want to stay very well hydrated. Also, as it can cause photosensitivity of the skin it is best to avoid potentially damaging exposure to sunlight or artificial UV rays.
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual and should not be construed as such.
Helpful?
Regards,
DocVikingo