[header] How to stop a rash from itching [title] Use a cold compress on the rash. [step] Application of cold causes temporary numbness of the nerve endings leading to reduced sensation. It soothes the skin and reduces the urge to itch. 
Less itching means less skin irritation and reduced development of rash, too. [substeps] Put some ice cubes in a plastic bag or towel and hold it on the itchy skin for a few minutes.