What causes a mouth ulcer to turn black?

The causes of oral ulcers turning black may be multifaceted. 1. It could be due to the absorption of necrotic tissue or bleeding from the ulcer surface, which causes blood accumulation and results in a black appearance. 2. If an oral ulcer develops a secondary infection, especially with anaerobic bacteria, it may produce black, putrefactive material, causing the ulcer surface to darken. 3. Long-standing ulcers that fail to heal may undergo malignant transformation when the body's immunity declines. In such cases, the ulcer may appear black and emit a foul odor, accompanied by severe pain. 4. Pigmentation may also be a contributing factor. Inflammation associated with oral ulcers can lead to localized pigmentation, resulting in a darker appearance. If you have any concerns, it is recommended to seek timely medical attention for diagnosis and treatment by a qualified healthcare professional.