Skin surface pain in the left thigh may be caused by herpes zoster, cryptococcal dermatitis, trauma and other causes, need to be analyzed according to the symptoms. 1. Herpes zoster: caused by varicella zoster virus (VZV) infection, herpes zoster rash can have weakness, fever, lack of appetite and other systemic symptoms before the rash, the affected area of the skin can have burning or burning pain, touching has obvious pain sensitivity. 2. Cryptosporidium dermatitis: contact dermatitis caused by skin contact with the venom in the body of the cryptosporidium. A few hours to 2 days after contact with the venom, localized stripes, flakes or dot clusters of edematous erythema with dense papules, blisters and pustules, part of the damage center of the pustules fused into a piece, which can be followed by vesicular erosion, scabbing and epidermal necrolysis, with itching, burning pain and burning sensation. 3. Trauma: the skin surface is sharp knives or contact with the surface of sharp objects, the thigh skin nociceptive nerve fibers are stimulated, afferent nerve center, which leads to the production of pain. There may also be other reasons for the skin surface pain in the left thigh, it is recommended to go to the hospital, under the guidance of the doctor for treatment.