The hair loss and redness on the dog's nose may be caused by mosquito bites, external parasites, fungal infection, or bacterial infection. You need to check whether there are parasites on the dog. If there are parasites, you need timely help. The dog is dewormed externally and anti-inflammatory drugs are applied to the affected area; if the affected area appears red, swollen, itchy, dandruff, scabs, etc., it may be a fungal bacterial infection, and the dog needs to be treated with fungal and bacterial drugs.