The skin is located on the surface of the body, wrapping the entire body, and is the boundary between the internal and external environment of the body, and is also the largest organ of the body. In addition to its barrier, absorption, sensory, secretion and excretion, thermoregulation, and material metabolism functions, the skin is also an important immune organ, participating in the body’s immune response and playing an immune surveillance role. When a skin disease occurs, our skin will play an immune role and there will be significant feedback, with itching, pain, burning, numbness, foreign body sensation, redness, swelling and erosion of the skin. However, abnormal skin manifestations may not be just a simple skin problem. Since there is also a close connection between the skin and other systems or organs of the body, internal disorders can have a complex effect on the skin, so skin abnormalities can often be the result of some internal pathology of the body as well. Pain, burning, numbness, etc. cause greater irritation and are easy to notice and pay attention to, and seek timely medical attention. Itchiness, on the other hand, causes less irritation and can easily be ignored. Simple skin diseases can cause itching, here is a list of some common diseases: Hives: pins and needles, crispy itching, burning sensation, usually more pronounced in the evening or at night. Scabies: papules, blisters and tunnels on tender areas of skin, pruritic nodules on the scrotum, characterized by increased itching at night. Eczema: the acute phase has a tendency to exude, while the chronic phase is infiltrative and hypertrophic. The lesions are polymorphic, symmetrical, itchy, and prone to recurrence. Autoimmune diseases: Some of these diseases have symptoms in the skin, such as dermatomyositis and lupus erythematosus. SLE may have fever, facial erythema, joint pain, hair loss, mouth ulcers, and may occasionally feel itchy and burning skin. Pruritus has been reported in 45% of patients with SLE. Dermatomyositis skin symptoms include purplish papules, dilated capillaries, and possible photosensitivity and pruritus. One study showed that 38% of children with dermatomyositis had pruritus. In addition to the above-mentioned skin diseases, some internal diseases can also cause itching, so when the following symptoms occur, you need to pay more attention and seek early medical diagnosis: 1. itchy and yellow skin, this is considered to be probably caused by liver disease, due to the high concentration of bile acids, which can precipitate in the skin and lead to severe itching; 2. itchy and dry skin, low urine, frequent urination, urinary urgency and back pain, you need to check the kidneys to prevent chronic nephritis or uremia (about 25% of chronic kidney disease has itching symptoms), because high calcium and phosphorus concentrations in the blood can also lead to itchy skin; 3. Skin itching is significantly worse at night, check the thyroid gland to prevent thyroid disease. Severe generalized itching may be one of the complaints of patients with hyperthyroidism and can also be seen in patients with hypothyroidism. Some studies have found complete or partial relief of itching in some patients after thyroidectomy; 4. Check blood sugar to prevent diabetes if skin itching persists for too long. The body’s ability to prevent germs is reduced in diabetic patients, making them susceptible to bacterial and fungal infections that induce pruritus. 70% of patients will have multiple skin conditions and skin manifestations. Restricted pruritus, especially in the genital and perianal areas, is more common in women with diabetes and is mostly associated with poor control of diabetes. One study found that vulvar itching was significantly more common in women with diabetes (18.4%) than in the healthy control population (5.6%); 5. Vulvar itching is more pronounced or lasts longer before and after the menstrual period, with the possibility of HPV infection, and should be checked for HPV to prevent vulvar basal cell carcinoma and cervical cancer. This is a condition that many women often do not pay enough attention to, and sometimes miss the diagnosis for months or even years, and only give routine anti-inflammatory and antifungal treatment, leading to the aggravation of the disease.