Medicinal Plants, Secondary Metabolites, and Their Antiallergic Activities

One of the significant health issues that plague people all over the world is immunological dysfunction, which includes allergies. Allergens include things like pollen, dust mites, food, cosmetics, animal fur, mold spores, and airborne particles from the environment. Mast cells and basophils release vasoactive amines, which are pharmacologically active mediators, as a result of the crosslinking of the bound IgE caused by a second exposure to the allergen. Vasodilation, increased vascular permeability, and smooth muscle contraction are all brought on by these mediators. Hexosaminidase is an enzyme that is typically secreted together with histamine when granules in mast cells or basophils degranulate. The rat basophilic leukemia (RBL-2H3) cell line uses this enzyme as a biomarker for antigen-induced degranulation. In recent decades, there has been a significant increase in the prevalence and severity of allergic disorders such as allergic conjunctivitis, allergic rhinitis, asthma, anaphylaxis, atopic eczema, food, drug, and insect allergy, as well as urticarial and angioedema. Many ailments have been treated with plants in traditional natural medicine. Numerous oriental medicinal plants in particular have been discovered to exhibit antiallergic action both in vitro and in vivo. Although their effectiveness and safety have not been scientifically established, medicinal plants have been used traditionally to treat allergy symptoms. Plant polyphenols have potent antiallergic properties and are a crucial source for the development of antiallergic medications. In this chapter, we compile the recent studies on the antiallergic effects of many medicinal plants and their secondary metabolites on the immune system.