Slight numbness of the outer thigh of the left foot needs to be treated according to the cause of the disease, generally there is rest, the use of methylcobalamin and other neurotrophic drugs, pain can be used ibuprofen and other pain relieving drugs and other methods. 1. Allergy: due to allergy to some items caused by local skin rashes and other changes, can cause slight numbness of the lateral thigh of the left foot, the treatment of the first detachment from the allergenic substances, rinsing, if necessary, the use of loratadine and other anti-allergy drugs. 2. Trauma: for the trauma caused by local cutaneous nerve injury caused by the left foot thigh lateral slight numbness, the treatment can be used to rest, the use of methylcobalamin and other neurotrophic drugs, pain can be used to use ibuprofen and other pain medications. 3. Lateral femoral dermal neuritis: Lateral femoral dermal neuritis caused by various reasons can be treated with vitamin B1, methylcobalamin and other neurotrophic drugs. 4. Lumbar intervertebral disc herniation: for the lumbar intervertebral disc herniation caused by nerve compression caused by the left foot and thigh lateral numbness, the treatment is mainly conservative treatment, such as bed rest, local microwave physiotherapy, anti-inflammatory drugs such as celecoxib, and if necessary, feasible surgical treatment. Slight numbness of the left thigh is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, give targeted treatment or treatment. The use of the above drugs need to comply with medical advice.