Final answer:
Intradermal injections are preferred for allergy skin testing, as they allow for the observation of a wheal-flare response to determine a type I hypersensitivity reaction. The correct option is 1.
Step-by-step explanation:
For allergy skin testing, the preferred injection is an intradermal injection. This involves injecting allergen extracts directly into the dermis layer of the skin using a small needle or a tuberculin needle. Following the intradermal test, the area is observed for a wheal-flare reaction within 15-20 minutes to determine a type I hypersensitivity reaction.
This diagnostic method is crucial for identifying specific allergens responsible for allergic responses and is used prior to considering treatments such as immunotherapy or desensitization therapy, which includes gradually increasing allergy shots with the aim to desensitize the patient's immune system over time. Hence, 1 is the correct option.