The following symptoms may occur after a hornet sting: 1) Serious local symptoms, hornet toxicity, local numbness, swelling, pain, ulceration, yellow water, etc. Sometimes the swelling may spread to the surrounding tissues, resulting in swelling of the whole arm or leg. 2) Neurological damage after a hornet sting, headache, dizziness, facial numbness, tongue numbness, blurred consciousness and blurred vision. The first thing you need to do is to get a good idea of what you are getting into. The best thing to do is to go to the hospital after being stung by a hornet.