My favorite for any insect bite is MSM lotion. (Mosquitos and Buffalo gnats love me and think I'm their all-you-can-eat buffet every time I walk outside

) I buy the NOW brand at my local health food store. For me, it will stop itching and swelling within the hour and the bite heals fast after that.
You can make a paste of baking soda and water and apply for some relief, and I have even used toothpaste.