Allergy and Its Remedies from Marine Sources

Allergy (allos = other, different, strange + ergon = activity) is a hypersensitivity disorder of the immune system (Michelle 2010). It is defined as the hypersensitivity to a substance that causes the body to react to any contact with an allergic substance. Allergy is one of the four forms of hypersensitivity and is formally called type I hypersensitivity, which in turn is classified into immediate and late-phase reaction. The immediate hypersensitivity reaction occurs minutes after exposure and includes release of vasoactive amines and lipid mediators, whereas the late-phase reaction occurs 2–4 hours after exposure and includes the release of cytokines. If these reactions are ignored, the entire body gets involved with allergic consequences and then anaphylaxis can take place, which is an acute, systemic reaction that can prove to be fatal. Allergy can be of many types depending on the etiological factor of the outside environment surrounding the human beings (Table 27.1). These factors affect an individual minimally as well as drastically depending on the individual’s genetically triggered immunity level. Environmental as well as genetic factors are involved in the triggering of allergy, which lead to various inflammatory responses in human body (Ayers et al. 2008). In general, following exposure to allergens, acute allergic sensitization involves the expansion of T-helper (Th)2 cells that secrete a multitude of cytokines interleukin (IL)-4, IL-5, IL-9, and IL-13 as well as chemokines such as thymus and activation-regulated chemokine and macrophage-derived chemokine, further leading to Th2 cell recruitment and activation of B cells (Muzzarelli 2010). B cells produce allergen-specific immunoglobulin E (IgE) that circulates and binds to mast cells and basophils; this consequence is influenced by IL-4. Further exposure to the allergens results in the crosslinking of IgE on mast cells and basophils causing degranulation of cells, release of several mediators like histamine, proteases, chemokines, prostaglandins, leukotrienes, and so on (Figure 27.1). Inhalation of allergens trigger bronchoconstriction through the recruitment of activated eosinophils, neutrophils, lymphocytes, and macrophages that lead to asthma, characterized by bronchial wall remodeling, hyperresponsiveness, and chronic inflammation of airways (Larche, Robinson, and Kay 2003). Detailed information about the types of mediators and their roles is listed in Table 27.2. Although treatment of allergy usually involves various drugs containing epinephrine, antihistamines, and corticosteroids, there is great interest in searching for antiallergic compounds and CONTENTS