Final answer:
Subcutaneous immunotherapy is the administration of an allergen via injections under the skin to desensitize the immune system, whereas sublingual therapy is a needle-free option that involves placing an allergen tablet under the tongue for absorption.
Step-by-step explanation:
The difference between subcutaneous immunotherapy and sublingual therapy primarily lies in their routes of administration and the mechanisms they use to desensitize the immune system. Subcutaneous immunotherapy involves the injection of increasing amounts of an allergen under the skin to gradually desensitize the immune system to that allergen, often used for treating environmental allergies or insect stings. On the other hand, sublingual therapy, involves placing a tablet containing the allergen under the tongue where it dissolves and is absorbed by the mucous membranes, making it a needle-free option that is generally used for allergies to specific substances such as grass pollens or house dust mites.