PURPOSE: To provide an agent for preventing generation of ammonia from urea under the presence of urease by using an urease inhibitor extracted from Rscus acule atus, Psidium quayava, Rosa rugosa, Rubussuavissimus, Artemisia princeps, Tamarindus indica, and Eribotrya japanica or the like, as an effective component.

CONSTITUTION: In enzyme urease produced by microorganism in excrements, urea in urine excreted from the human body reacts with water so as to produce ammonia and carbon dioxide gas, and thus produced ammonia increases the pH value of the skin so as to tend to cause diaper rash. Accordingly, natural urease inhibitor which is highly safe and easily usable, is extracted from Rscus acule atus, Psidium quayava, Rosa rugosa, Rubussuavissimus, Artemisia princeps, Tamarindus indica, and Eribotrya japanica or the like. Concentrate obtained by only removing an extracting solution from the this extract or a dry substance thereof is directly used as an ammonium generation preventing agent, or is dissolved in water, water-containing alcohol, 1,3-butylene glycol or the like so as to obtain a liquid solution or a power-like material.