Prunellae Spica is in use in Korean medicine. Korean medical doctors use Prunellae Spica for removing heat and fire(淸熱瀉火), etc. We investigated toxicity, poisoning symptoms, poisoning treatment, side effects and prevention against poisoning of Prunellae Spica. The results were summarized as follows: 1. Prunellae Spica did not show the special toxicity in the toxicity experiment. But side effects and hypersensitivities of Prunellae Spica have been reported by clinical experience report. The medication of Prunellae Spica can cause eruption, itching, nausea, rapid pulse, dizzy, stomachache, diarrhea, etc by side effects. And the medication of Prunellae Spica can cause eruption on the skin and stimulation on mucous membrane of the throat by hypersensitivity. 2. In the case of occurrence of side effects and poisoning. The representative treatment methods are stopping medication, and symptomatic treatment, etc. 3. In order to prevent against poisoning of Prunellae Spica, the patients should keep usage, dosage and notes.