There are no authoritative studies showing the side effects of drinking knotgrass in boiled water. However, knotgrass boiled water can precipitate less medicinal ingredients, with limited efficacy and effect, so it is recommended to take it by decoction. You should standardize the use of Chinese herbal medicines under the guidance of a doctor’s diagnosis to prevent medication hazards. Polygonum aviculare has the effects of diuretic and diaphoretic (to improve the problem of dribbling of urine, small amount of urine and inability to pass), insecticide, and antipruritic. Polygonum aviculare is bitter in taste and slightly cold in nature. Polygonum aviculare can be used in the treatment of feverish gonorrhea (burning and tingling during urination, accompanied by frequent urination and urgency, and discomfort in the abdomen), astringent pain, short and red urination (small amount of urination, dark yellow in color), and abdominal pain of worms and other conditions. If treating hemorrhagic gonorrhea (the appearance of blood in urine with pain), it is suitable to be used with artichoke, bupleurum root, pueraria lobata, etc. to cool blood and stop bleeding; if treating gravel gonorrhea, it can be used with moneywort, hijinsha, huzhi, etc. to clear the gonorrhea; ureteral stones with pyelonephrosis can be treated with knotgrass in combination with hijinsha, slippery rock, dioscorea.