There are many reasons for itching in the back of the knee socket, usually eczema, atopic dermatitis, ringworm or pimple urticaria, and it is necessary to consult a doctor in time for a clear diagnosis. 1. Eczema is caused by allergies, eczema in the back of the knee fossa is usually localized skin contact with mites, pollen, dust and other items caused by allergic reactions, you can do an allergen test to clarify the body allergens. 2. Atopic dermatitis is related to immune system disorders and allergies, and has a clear genetic predisposition. Atopic dermatitis body is mostly allergic, easy to produce systemic allergic reactions, especially in the limbs, neck, face. 3. Ringworm is caused by fungal infection, and many ringworms in the back of the knee nest are infected by animals. The metabolites produced by the fungus can irritate the skin and produce an itchy sensation. 4. Papular urticaria is an inflammatory reaction of the skin caused by insect bites, and most of the insect bites at the knees are flea and midge bites. The cause of the itching behind the knee fossa more symptoms continue to do not relieve, you can consult a doctor in a timely manner, in accordance with the doctor’s instructions for treatment.