Oscillococcinum (commonly shortened to Oscillo) is a homeopathic alternative medicine marketed to relieve influenza-like symptoms. It is a popular homeopathic preparation, particularly in France. Oscillococcinum is manufactured by a French company, Boiron, its sole manufacturer. There are, however, other manufacturers who make similar preparations. Oscillococcinum is used in more than 50 countries. In France, it has been in production for over 65 years.

The preparation is derived from duck liver and heart, diluted to 200C—a ratio of one part duck offal to 10400 parts water. This is such a high dilution that the final product likely contains not a single molecule of the original liver. Homeopaths claim that the molecules leave an "imprint" in the dilution that causes a healing effect on the body, although there is no evidence that supports this mechanism or efficacy beyond placebo.

A class action lawsuit on behalf of customers who purchased Oscillococcinum was filed against Boiron in the United States, alleging that Boiron falsely advertises that Oscillo has the ability to cure the flu; Boiron settled the case for $2m.

Origin and history
The word Oscillococcinum was coined in 1925 by the French physician Joseph Roy (1891–1978) who saw military duty during the Spanish Flu epidemic of 1917. Roy wrote that on examining the blood of flu victims, he had observed an oscillating bacterium which he named Oscillococcus.

Roy claimed he had detected it in the blood of patients that had several viral diseases like herpes, chicken pox and shingles. He thought that this bacterium was the causative agent of diseases as varied as eczema, rheumatism, tuberculosis, measles, and cancer. Believing he had detected it in the blood of cancer patients, he tried a vaccine-like therapy on them, which was unsuccessful. Medical science has since disproved Roy's theory: rheumatism, for example, is not caused by bacteria, and measles is caused by a virus far too small for Roy to have observed in his optical microscope.

The oscillococcus bacterium has never been independently observed.

He searched for the "bacterium" in several animals until he felt that he had found it on the liver of the Long Island duckling. The modern preparation is created from the heart and liver of Muscovy Duck (see the preparation section for the details).

In France the selling of all products manufactured according to the Korsakovian principle of dilution was forbidden until 1992, with the exception of Oscillo, thanks to a special measure made for it. As of 2000 Oscillococcinum was one of the top ten selling drugs in France, was publicised widely in the media, and was being prescribed for both flu and cold. As of 2008 it sells US$15 million per year in the U.S., and it also sells widely in Europe.

Preparation
The ingredients of a one gram tube of Oscillococcinum are listed as:
●Active ingredient: Anas Barbariae Hepatis et Cordis Extractum (extract of Muscovy Duck liver and heart) 200CK HPUS 1×10−400 g
●Inactive ingredient: 0.85 g sucrose, 0.15 g lactose (100% sugar.)

The 200CK indicates that the preparation entails a series of 200 dilutions of the starting ingredient, an extract from the heart and liver of a Muscovy Duck. Each step entails a 1:100 dilution, where the first mixture contains 1% of the extract, the second contains 1% of the first mixture, etc. The K indicates that it is prepared by the Korsakovian method, in which rather than 1% of the preparation being measured out at each stage and then diluted, a single vessel is repeatedly emptied, refilled, and vigorously shaken (in homeopathic terminology "succussed"), and it is assumed that 1% remains in the vessel each time. The 200C dilution is so extreme that the final pill contains none of the original material. Mathematically, in order to have a reasonable chance to obtain one molecule of the original extract, the patient would have to consume an amount of the remedy roughly 10321 times the number of atoms in the observable universe.

In the United States, under the 1938 Federal Food, Drug, and Cosmetic Act, only those substances listed in the Homeopathic Pharmacopeia of the United States (HPUS) and prepared according to the guidelines therein may be marketed as homeopathic. Only preparations of Oscillococcinum made according to those guidelines may be thus labeled. "A product's compliance with the requirements of the HPUS, USP, or NF does not establish that it has been shown by appropriate means to be safe, effective, and not misbranded for its intended use."

Oscillococcinum is generally considered harmless. When Boiron's spokeswoman Gina Casey was asked if a product made from the heart and liver of a duck was safe, she replied: "Of course it is safe. There's nothing in it."

Efficacy
There is no scientific evidence that Oscillococcinum has any effect beyond placebo. None of its active ingredient is present in a dose of the final product, nor is there any credible evidence that duck liver is effective in relieving flu symptoms in the first place. Homeopaths claim the diluted molecules leave an "imprint" in the remedy, but there is no known mechanism for how this could occur. Homeopathy as a whole is considered to be pseudoscience.
Since it is used for the relief of symptoms of flu, a disease that goes away on its own in a variable number of days, the best it could do is shorten the duration of those symptoms. If one takes any medication and one's flu goes away, then it is easy to attribute this to the medication; however, the infection would have resolved anyway. Someone who gets over a mild strain of flu will attribute the mildness to the efficacy of the homeopathic preparation and not to the fact that it was a mild strain, and will recommend it to other people, spreading its popularity. Also, the most likely explanation for its effectiveness with flu symptoms is that patients are misdiagnosing the symptoms of several rhinovirus diseases or of allergies to several hundred substances, and attributing them to a flu infection that they do not have.

A 2002 review says that the evidence for Oscillococcinum's effectiveness concludes that no homeopathic preparation is relevantly different from placebo or superior to other treatments. A 2003 review from the U.S.'s National Institutes of Health found that, in general, systematic reviews of homeopathic preparations have not found homeopathy to be a definitively proven treatment for any medical condition. A 2005 review of flu treatments (vaccine, medicine, homeopathy) has concluded that the popularity of Oscillococcinum in France was unsupported by the current evidence as to its efficacy. In a 2007 review, the effectiveness of non-mainstream remedies against seasonal flu could not be established beyond reasonable doubt, and the evidence is found to be sparse and limited by "small sample sizes, low methodological quality, or clinically irrelevant effect sizes", and that the results strengthen using conventional approaches for flu.

A Cochrane review published in December 2012 found that there was insufficient evidence to make a robust conclusion about whether Oscillococcinum is effective for the prevention or treatment of influenza.

Criticisms of marketing
The non-profit, educational organizations Center for Inquiry (CFI) and the associated Committee for Skeptical Inquiry (CSI) have petitioned the U.S. Food and Drug Administration (FDA), criticizing Boiron for misleading labeling and advertising of Oscillococcinum. "One petition complains that Boiron’s packaging for Oscillococcinum lists the alleged active ingredient – duck liver and heart – in Latin only. Another petition complains that Boiron’s web ad for this product implies that it has received FDA approval." Ronald Lindsay, CFI and CSI president and chief executive officer, contends, "If Boiron is going to sell snake oil, the least they can do is use English on their labels.”
A class action lawsuit has been filed against Boiron on behalf of "all California residents who purchased Oscillo at any time within the past four years." The lawsuit charges that Boiron "falsely advertises that Oscillo has the ability to cure the flu because it contains an active ingredient it claims is proven to get rid of flu symptoms in 48 hours." The lawsuit also states that the listed active ingredient in Oscillococcinum (Oscillo) "is actually Muscovy Duck Liver and Heart...and has no known medicinal quality." A settlement was reached, with Boiron denying any wrongdoing. As part of the settlement, Boiron has agreed to make specific changes to its marketing. These changes include adding to their packaging notices like "These ‘Uses’ have not been evaluated by the Food and Drug Administration" and "C, K, CK, and X are homeopathic dilutions."