A 35-year-old woman presents to the primary care office with a history of nasal congestion that has worsened over time and recurrent sinus infections. She considered herself healthy until about 12 months ago when she began experiencing rhinorrhea, sneezing, and nasal stuffiness that "seems to never go away". She noticed that her rhinorrhea greatly improved when she attended her family reunion on a two-week Caribbean cruise but returned after being home a few days. She lives with her husband and 5- year-old child. They have two household pets: a dog that has lived with them for the last 4 years and a cat who joined the family 1 year ago. Pathophysiology & Clinical Findings of the Disease 1. Identify the correct hypersensitivity reaction: The likely diagnoses of this patient would be allergic rhinitis (AR), however there are methods, diagnostic procedures and tools used to determine a clear diagnosis for this patient such as: screening the patient’s medical and family history, collection of genetic factors and environmental factors. The patient may obtain a skin prick test, patch test or intradermal test through an allergist to determine their sensitivities (American College of Allergy, Asthma, and Immunology, 2020). 2. Explain the pathophysiology associated with the chosen hypersensitivity reaction: Allergic rhinitis, also known as hay fever, includes symptoms which affect the nose. It occurs when the body recognizes something in the environment and overly reacts. This hypersensitivity is considered an immune response. There are four types of hypersensitivity reactions: type I (IgE-mediated reactions), type II (tissue-specific reactions), type III (immune complex–mediated reactions), and type IV (cell-mediated reactions). Many allergic reactions like allergic rhinitis are considered type I (IgEmediated reactions). The first exposure to an allergen causes a presentation of the antigen-presenting cell to B lymphocytes, which is considered the followers of T-cells (Th2 cells). These Th2 cells produce cytokines that assist in maturation of the B lymphocytes into plasma cells that secrete IgE. The IgE is absorbed to the surface of the mast cell by binding to specific IgE Fc receptors. When there is a significant amount of IgE bound to the mast cell it then becomes sensitized. When an individual is re-exposed to the the allergen, the allergen ultimately cross-links the IgE that’s bound to the mast cell and causes degranulation of the mast cell. The mast cell then induces a reaction which causes histamine in the body to react inducing local edema, mucous secretion, smooth muscle contraction and other acute inflammatory responses (McCance, K. L., & Huether, S. E., 2019). Regarding the case study the 35-year-old woman presented with nasal congestion and recurrent sinus infections, she noticed a great improvement when she went on a two-week Caribbean cruise when she was no longer exposed to the allergen,