Advertising claims about medicinal products are judged particularly strictly under competition law. This includes the principle that advertising may only be based on statements that correspond to established scientific knowledge. Particular caution is therefore required with such advertising. The Federal Court of Justice has clarified that the required established knowledge must already exist at the time of advertising. For the advertiser’s own security, this should be well documented. It is not sufficient if a company only wants to prove in a later process by an expert that the statement was so certain: Anyone who only has to obtain expert opinions on this later has also advertised with an unsubstantiated statement at the time of advertising (BGH, judgment of 5 November 2020, ref.: I ZR 204/19).