Intense itching is a symptom and not a disease. The only tissues that can cause itching are the skin, mucous membranes, and cornea. Itching is a major symptom of many skin diseases and is also seen in many systemic diseases. Skin diseases that often cause severe itching include: scabies, urticaria and lichen planus, and many others, so patients need to be examined in detail when treating severe itchy skin so that the cause of severe itchy skin can be determined in a timely manner. Laboratory tests for severe itching of the skin caused by scabies: I. Needle picking method This method is applied to lesions that are tunnels or blisters. First, the tunnel should be carefully observed, and then the yellowish worm spot should be identified at the blind end. Use a sterilized needle to pierce from the side and pick out the worm at its base, then place it on a slide and examine it with a magnifying glass or microscope. In case of blisters, the worm spot can be found at the edge of the blister, and it can be picked out for examination according to the above method. Skin scraping method Select early papules, drop a little paraffin oil or common mirror oil on the lesions, then scrape a few times with a surgical knife on the surface of the lesions until small blood spots appear in the oil, and finally move to an oil slide for microscopic examination. Microscopic examination Add a drop of mineral oil or common mirror oil on the lesion to be examined, and then shoot a strong light source (high-pressure mercury lamp) at an angle of 45 degrees, followed by direct observation and examination under a low-powered microscope. Four, filtered ultraviolet lamp examination first in the tunnel lesions coated with 0.1% tetracycline solution, dry with distilled water cotton ball wipe clean, and then placed under the lamp, such as the tunnel is bright green fluorescence is positive.