Wood fungus is divided into dry fungus and fresh fungus. Generally, dry fungus soaked overnight is not toxic per se, but it is susceptible to bacterial contamination and toxic ingredients when the ambient temperature is high during the soaking process, while fresh fungus itself has some toxicity, so it may be toxic when soaked overnight. Most of the fresh fungus contains porphyrins, which are light-sensitive chemicals that can be absorbed by people and cause sun-dermatitis, rashes, and even breathing difficulties. In the process of processing fresh fungus into dried fungus, most of the porphyrins are destroyed and decomposed. After forming dried fungus, it contains only a small amount or almost no porphyrins, and even if it is absorbed by the human body, there is usually not much reaction, so the processed dried fungus itself is non-toxic. The long-eating fungus is made from dried fungus soaked in water, and since dried fungus is non-toxic, soaking it in water overnight usually does not produce toxicity. Although dried fungus is non-toxic, it is susceptible to environmental factors during the soaking process, which can cause contamination by bacteria, mold and other microorganisms and produce toxins that may cause diarrhea, vomiting and other toxic reactions after consumption. Therefore, it is recommended that the process of soaking fungus should not take too long and the temperature of the environment should not be too high. Do not eat any fungus that has a bad smell or is rotten. If you have an abnormal reaction after eating it, you should seek medical attention immediately to avoid serious consequences.