Protozoa are unicellular eukaryotic animals, tiny in size but capable of independently accomplishing all physiological functions of life activities. They are widely distributed in the natural world, with a great variety of species. So far, more than 65,000 species have been found, most of which are autochthonous or saprophytic life, distributed in the ocean, soil, water or decay, about nearly 10,000 species of parasitic protozoa, living in the animal body or the body surface, in addition to a small number of medical protozoa.

Fecal examination is a common pathogenetic test for the diagnosis of parasitic diseases. Commonly used methods include direct smear method and thick smear transparency method. Protozoa encapsulation staining solution (2% iodine solution) is a kind of direct smear method, which is an aqueous solution of iodine and potassium iodide, similar to Lugol's iodine solution, and is mostly used for fecal examination of helminth eggs, protozoa encapsulation and trophozoites; the effective content of iodine in it is 2%, which is simple to operate, and it can be sampled and examined for many consecutive days, which improves the detection rate, but the negative result completely excludes parasitic infection.

Mainly composed of iodine, potassium iodide, iodine solution concentration of 2%, mainly used for fecal samples of protozoa in the encapsulation of staining.