Saint Ignatius Itch is the name given to a persistent itch that is hard to scratch. There are several synonyms for this irritating condition, including Pruritus, Tingling, Crawling sensation, Reef Itch and Heat rash. Pruritus is a common term used to describe any irritating sensation of the skin that causes a strong desire to scratch. Tingling is a prickling sensation that is often associated with numbness or pins-and-needles. Crawling sensation is an uncomfortable feeling that is similar to something crawling on the skin. Reef Itch is an itchy rash that commonly affects divers and swimmers. Heat rash is also known as miliaria, and is caused by excessive sweating leading to blocked pores.