This is, as usual, a hybrid of info from several sources, and I don't vouch for it being a panacea, but it is very similar to commercial calamine lotion, which certainly comes in handy after a camping trip ridden with mosquitoes, as I unfortunately just experienced.
Take 1 tbsp unscented kitty litter and grind to a powder in the food processor or coffee grinder. Add 1 tbsp baking soda, 1 tsp sea salt, and 1 tsp zinc oxide. Add water until it forms a paste. Add a few drops of peppermint and eucalyptus oil (perhaps like, 1 drop of each. I went with a liberal sprinkle and currently feel a little more tingly than I'm comfortable with.) Apply to affected skin.
The one active ingredient that commercial calamine lotion has that this doesn't is iron oxide, which is usually only 5% to 95% zinc oxide, and which I omitted because I don't think it's possible to buy or make it. The zinc oxide is the main ingredient, as it soothes, dries, and heals damaged skin. The kitty litter is made of bentonite clay, which absorbs impurities in the skin, and the salt and baking soda reduce itching. I'm not sure what the essential oils are doing besides setting me on fire, but calamine usually does give you that hot-cold sting, so perhaps it's serving some purpose. At the very least, it's a sensation which distracts from the itching!
The resulting goop will be grey rather than pink.