Final answer:
A patch test is a method used to identify allergies to substances by applying them to sensitive skin areas such as behind the ear or on the inside of the elbow and observing for reactions.
Step-by-step explanation:
A patch test is generally conducted behind the ear or on the inside of the elbow. This type of test is used to identify allergies to substances like perfumes, latex, medications, and various other products. By applying a small amount of the substance on the skin in these areas, where the skin is relatively thin and sensitive, healthcare providers or allergists can observe any allergic reactions that may manifest within 48 hours. This method is crucial for identifying allergens that may cause contact dermatitis and other allergic reactions. It's a preventive measure before full exposure to a potential allergen.