Itchy blisters at the knees may be caused by ringworm or eczema, and the cause should be treated after a clear diagnosis. 1. Ringworm: caused by dermatophyte infection, may manifest as pimples, blisters or papules, itching and other symptoms. Treatment includes topical and oral antifungal drugs, such as oral terbinafine or itraconazole, and topical ketoconazole cream. 2. Eczema: A variety of internal and external factors such as decreased immunity or external stimuli lead to eczema, resulting in itching, blisters and other symptoms. Treatment can be oral antihistamine drugs such as loratadine to relieve itching, blisters are larger and more, the blisters will be drawn out of the fluid with a wet compress of boric acid solution, such as blisters are not big, can be used externally with zinc oxide treatment. The blisters on the knee with itching, do not scratch, it is recommended to consult a doctor in time to clarify the cause of the disease, symptomatic treatment.