Possible causes of itchy elbow and knee joints include mosquito bites, allergic reactions, eczema and so on. 1. Mosquito bites: Due to lack of protection, elbow and knee joints are bitten by mosquitoes, and after mosquito bites, localized rashes may appear, causing itching, which is a normal phenomenon. 2. Allergic reaction: due to contact with certain allergens, such as seafood, pollen, dust, mites, etc., causing an allergic reaction to the body, there can be a large area of itchy skin. 3. Eczema: due to the body contact with dust, dust mites, chemical substances, etc., caused by the skin inflammation reaction, can appear in many parts of the body spots, blisters, pimples, etc., mostly accompanied by itchy skin. Causes of elbow and knee joints on the inside of the itch is more reasons, but also may be related to contact dermatitis, urticaria, psoriasis and other diseases, if the symptoms continue to be unrelieved, it is recommended to consult a doctor in a timely manner, to clarify the cause of the disease, and targeted treatment.