Black stool symptoms do not usually occur when you take Phellodendron Bark. Dark stool symptoms may be caused by eating foods such as animal offal or spinach, taking dark-colored medicines, or internal bleeding. If you experience dark stools while taking Phellodendron Bark, seek medical attention as soon as possible to determine the cause. Phellodendron Bark is a heat-clearing and dampness-drying herb with a bitter taste and cold nature, which belongs to the kidney and bladder meridians. Its main effects include clearing heat and drying dampness, removing fire and vapor, and detoxifying sores. It is mainly used to treat all kinds of damp-heat condensation (dampness and heat in the body and each other) in the lower Jiao evidence, such as damp-heat diarrhea, jaundice, yellow urine, itching in the pubic area; yin deficiency and internal heat caused by excessive sweating, spermatorrhea; sores and swelling due to the fire and heat; damp-heat and toxicity caused by eczema, and so on. Phellodendron Bark is bitter cold, easy to hurt the stomach qi, so the spleen and stomach cold people are prohibited, the specific use of drugs, please consult a professional physician.