As a preacher in Lyon and Bordeaux, Loyson acquired his reputation as the most effective pulpit orator of his day; and his success soon afterwards induced him to seek the more critical audiences of Paris, where Loyson further established his fame at the Église de la Madeleine and Notre Dame de Paris. Mullinger wrote that Loyson's "resonant voice and impassioned rhetoric possess, especially for his own countrymen, a powerful charm." His eloquence drew all Paris to his Advent sermons in Notre Dame de Paris between 1865 and 1869, but his orthodoxy fell under suspicion. In 1868, he was summoned to Rome and was ordered to stop preaching on any controversial subject, and to confine himself exclusively to those subjects upon which all Roman Catholics were united in belief.