What are the differences between oral- sublingual-, and dermal immunotherapy?

The different routes of immunotherapy dosing have different pros and cons. These considerations are explored here in relation to allergy immunotherapies. Allergies occur when the body’s immune response is overexaggerated when exposed to certain substances. Allergies are most commonly managed by avoiding exposure to the allergen, but immunotherapies have been designed to help modulate the immune system and suppress its reactivity over time. Most protocols consist of three phases: escalation, build-up, and maintenance.¹ Immunotherapy for allergies are most commonly used for developing a tolerance for food and is administered either orally, sublingually or dermally.² Oral immunotherapy is used to induce tolerance to a trigger food by administering minute amounts through the mouth. Using low doses induces desensitization, tolerance and sustained unresponsiveness over the long term with reduced incidences of future adverse reactions. Sublingual immunotherapy is most commonly used to target asthma and allergic rhinitis but is also used to treat food allergies. Small amounts of allergens are placed under the tongue for rapid entry into circulation without entering the stomach. Dermal immunotherapy involves the introduction of an allergen either percutaneously via the topical application or subcutaneously via injections underneath the skin. Dermal applications are most commonly used when testing for allergens, but this mode is now also being regularly employed for food allergy immunotherapy.

References:
1. R. Mir et al, "Immunosuppressive Agents and Their Role in Managing Immunotherapy Toxicities in Melanoma," Clin Skin Cancer 2(2): 18-23, 2017.
2. K.I. Nagaura et al, "Novel Immunotherapy and Treatment modality for Severe Food Allergies," Curr Opin Allergy Clin Immunol 17(3): 212-219, 2017.