Organon §157

A homeopathic aggravation is the medicinal disease, not a worsening of the original disease.

While it is certain that a homeopathically selected remedy, on account of its appropriateness and the smallness of its dose, quietly lifts and annihilates an acute disease that is analogous to it without amplification of its non-homeopathic symptoms (that is, without the arousal of newer, more significant ailments), it is nevertheless usual (but likewise only with a dose not properly diminished) for it to produce some kind of small aggravation in the first hour or few hours immediately following its ingestion. (The aggravation will last for several hours if the dose is somewhat too large.) This aggravation is so similar to the original disease that it appears to the patient to be an aggravation of his own malady. In fact, it is nothing other than a highly similar medicinal disease that is somewhat stronger than the original malady.