I believe that many people have heard the slogan “If you have grey nails, one infects two”, which does sound pretty scary, so let’s get to know grey nails together. Most people think that gray nails are nail fungus or nail fungus, but strictly speaking nail fungus and nail fungus are not exactly the same, nail fungus refers to the infection caused by dermatophytes invading the nail plate or nail tissue, while nail fungus is a nail infection caused by fungi such as dermatophytes, yeast and non-dermatophytes. Nail fungal disease is mostly caused by direct transmission of ringworm, and its susceptibility factors include: genetic factors, diabetes, and nail trauma. Nail fungal disease is often clinically classified into four types: white superficial type, distal lateral subxiphoid type, proximal subxiphoid type, and total nail destruction type. 1, white superficial type: is caused by fungal direct infection of the nail surface. It appears as a white cloudy nail plate with dotted or irregular shape, and the nail plate surface loses its luster. 2.Distal lateral subxiphoid type: It is often caused by the spread of tinea pedis. The fungus invades the lateral edge of the nail end from one side of the nail contour to make it thicken and cloudy. 3. Proximal subxiphoid type: The fungus enters the nail plate and nail bed from the nail tubercle. It often shows as nail root, nail half moon rough thickening, unevenness or destruction. 4, the whole nail destruction type: often manifested as the entire nail plate thickening, cloudy, nail bed surface residual keratinized accumulation, gray-yellow, gray-brown, seems to be decaying wood-like appearance. The disease generally has no conscious symptoms, nail plate thickening or destruction can affect the fine finger movements, affecting the patient’s aesthetics, but also unfavorable to wear shoes. The disease can be secondary to nail fungus, appearing as redness, swelling, heat and pain. Because of the slow growth of the nail, and the drug is not easy to enter the nail plate, so the treatment is more difficult, the key is to adhere to the medication. If there are no contraindications, oral antifungal drugs (such as itraconazole capsules, terbinafine tablets, etc.) can be taken. For superficial and uninvolved nail root damage, topical medication (such as ciclopirox nail coating, amorolfine nail coating, etc.) can be chosen for a course of 3 to 6 months or more until a new nail is produced.