Rash-------natural. There are thousands of different types of rashes. I have studied them for 50 yrs and still have much to learn. Poison ivy is natural. So is lead. Don't be fooled by "natural". You need to know what is effective and what is safe. "natural" is not relevant. To determine the best remedy for a rash you must first define it. I hope you find the correct diagnosis. Then you can get the best remedy.
Too many poss causes. There are so many different causes of skin rashes that it is difficult to answer this question. A ringworm-type rash needs completely different treatment than eczema. Some rashes are related to or caused by bacterial infections and treatment for them would be different too. A rash from scabies infection, a rash from poison ivy, a rash from the sun; all of these would have specific treatment.