The studies performed on oscillococcinum have been few.  The report of adverse events is rare and generally not a serious concern.  One trial (Papp 1998) reported a headache as an adverse event, "possibly related to the trial medication."  Another study (Ferley 1989) reported an adverse event rate of 3.2% overall, with no difference between groups.  As with all homeopathic medications, there is very little, if any, of the "active ingredient" in the final product.  Because of the many dilutions performed in the preparation of oscillococcinum, there is very little chance of adverse effects.  It is also unlikely to interact with other conditions or medications.

The ingredient list on the package lists that 1 gram of oscillococcinum contains:

0.85 g sucrose

0.15 g lactose

Active Ingredient: Anas Barbariae Hepatis et Cordis Extractum (extract of Muscovy Duck liver and heart) 200CK HPUS 1x10^-400g