A hypo spray, also known as a jet injector, is a medical device that uses high-pressure fluid to inject medications or vaccines into the body without the use of a needle. This technology is particularly useful for patients who are afraid of needles or who have a needle phobia. There are several synonyms for hypo spray, including simply "jet injector," "needle-free injection system," and "high-pressure injection device." Other terms that may be used in the medical field include "intradermal jet injector" or "subcutaneous jet injector." Whichever term is used, hypo sprays are a powerful tool for administering medication with minimal discomfort for the patient.