As soon as you receive a hornet sting, check if there is any stinger left inside the skin. Use a thin knife or credit card sharp edge to take out the stinger. Do not use a tweezers. Just press on the flat side of the sting so that the stinger pops out. Take off any jewellery or fabric from that part of the skin. It is very important that you remove the entire stinger so that it does not become a constant source of pain.
After you take out the stinger, pat the area with an ice cube. The ice has pain relieving properties as it numbs the area. It will also help in reducing any inflammation. If the itchiness is too much, take a local antihistamine to reduce it. Remember to keep the ice on the sting to help reduce the swelling and slow down the movement of the toxins under your skin. Although it might hurt by keeping ice on the sting, keep it on until the swelling subsides and the pain is slightly reduced.
If the pain is too much you can take a painkiller like acetaminophen or ibuprofen. However, such medicine is not advised for anyone aged under 18.
You can also use a home remedy of baking soda. Take a mixing bowl and add to it 2 tablespoons of baking soda and 2 tablespoons of water. Mix the ingredients well so that they are combined to make a thick solution. Now apply some of it on the sting directly using a spoon. Let this stand on the area until you feel some relief from the pain. This method might not work for some people but it does not hurt to try it out as it is easy to prepare with items that are found from around the house.