Allergy can be defined as a systemic immunological disease, wherein the immune system of the body reacts abnormally to a foreign substance. The foreign substance that triggers an allergic reaction is known as an allergen. Allergens are known to induce an immune response in human beings which are characterized by the presence of allergen-specific IgE antibodies. Allergic immunotherapy can be defined as the administration of allergen for the purpose of inducing tolerance specific to the allergen for the treatment of allergy. Allergy immunotherapy is a treatment that targets the underlying allergic disease, and affects the immunological mechanisms inducing immunologic tolerance. Allergies are caused due to exposure to various agents such as food, plants, pollen, and others. The various routes of exposure to allergens that lead to allergic reactions include inhalation, ingestion, skin contact, and injection. These allergens lead to a range of manifestations, including rhinitis, conjunctivitis, urticaria, and atopic dermatitis.