Itchy skin on the outside of the calf can be caused by papular urticaria, hives, eczema, ringworm and other diseases. 1. Pemphigus urticaria: can be caused by mosquitoes, fleas, cockroaches and other bites that trigger an allergic reaction, can occur on the outside of the calf scattered distribution of fusiform pimples, accompanied by itching discomfort. 2. Urticaria: After the occurrence of urticaria, itchy and reddish skin can appear on the outer side of the calf, which can rapidly develop into white or reddish red bumps with different shapes, which can cause itchy skin. 3. Eczema: after the occurrence of eczema on the lateral side of the calf, single or multiple round or irregular edematous erythematous spots, papules, etc., which can be crusted, flaky, etc., accompanied by itchy symptoms. 4. Ringworm: ringworm is an infectious skin disease caused by fungal infection, which is easily induced by local dampness, low immunity and diabetes mellitus, and may appear locally as ring-shaped or semi-ring-shaped erythema, and the skin may be flaky and itchy. Itchy skin on the outer side of the calf should be timely medical treatment, under the guidance of specialists to actively carry out the appropriate treatment, which will help to alleviate the uncomfortable symptoms as soon as possible.