Red: the nail bed is red, indicating qi-blood heat syndrome. Those who are ruddy are slightly ill, and those who are red and withered are seriously ill. Bleeding of nail bed also belongs to red nails. If there is spindle-shaped longitudinal linear bleeding on the free edge of the nail, it can be seen in coagulation dysfunction, drug allergy, subacute endocarditis and so on.
Yellow: the color of nail bed is yellow, suggesting damp-heat fumigation. Huang Liang suggested that the illness was mild and the course of disease was short. Dark yellow indicates a serious illness and a long course of disease. Yellow nails can be seen in hepatobiliary diseases, hemolysis, hypothyroidism, chronic adrenal insufficiency, nephrotic syndrome and carotene anemia.
Cyan: blue nail bed, suggesting cold syndrome, blood stasis, pain syndrome and convulsion. Found in hypoxia or using adipine and phenolphthalein. Long-term cyanosis and withering indicate that liver qi will fail and the prognosis is poor.
Black: The nail bed is black, indicating cold syndrome, blood stasis and pain syndrome. After a long illness, black nails appear and wither, suggesting that kidney qi will be exhausted and the disease is dangerous. One or several thin black vertical lines appear on the nail surface, suggesting endocrine disorders, which can be seen in menstrual disorders, dysmenorrhea, malignant tumors, radiation sickness and so on. After receiving radiotherapy and chemotherapy for cancer, each course of treatment can form a black mark on the nail, and each course of treatment has a circle record.
Blue: indicates that the liver is affected by pathogenic factors and blocked by blood stasis. Modern research has found that oral chloroquine, hexadiazepine, hemochromatosis, hepatolenticular degeneration, nitrite poisoning and hypoxia can lead to cyanosis.
Brown nail: common in acanthosis nigricans, adrenal hypofunction, or oral phenolphthalein, antimalarial drugs, etc.
Red and white nail: the distal nail is reddish brown, and the proximal deck is glassy white with clear boundaries, which is common in azotemia of liver cirrhosis.