PHCP312 Allergic Rhinitis Overview

Study Notes

Inflammation of nasal mucous membranes triggered by inhaled allergenic particles in sensitized individuals.
Two main types: Seasonal (hay fever) and Persistent (formerly perennial).

Airborne allergens are inhaled, processed by lymphocytes, leading to production of IgE in genetically predisposed individuals.
Re-exposure to allergens causes IgE bound to mast cells to trigger inflammatory mediator release.
Immediate reaction occurs seconds to minutes after exposure, mediated by histamine, leukotrienes, and other substances.
Key outcomes: Vasodilation, increased vascular permeability, and nasal secretions, resulting in symptoms like sneezing and nasal obstruction.
Late-phase reaction can occur 4 to 8 hours post-exposure, causing chronic symptoms like nasal congestion.

Type 1: Immediate hypersensitivity (IgE mediated) leading to allergic responses like anaphylaxis.
Type 2: Cytotoxic reactions involving IgG and IgM, occurring hours to days.
Type 3: Immune complex reactions involving deposits in blood vessels, manifesting in conditions like SLE and serum sickness.
Type 4: Delayed hypersensitivity mediated by T-cells, with examples including nickel allergy and poison ivy.

Seasonal allergic rhinitis caused by exposed pollens during specific seasons, leading to acute symptoms.
Persistent allergic rhinitis occurs year-round due to allergens like dust mites and molds, usually presenting with chronic and subtle symptoms.
Intermittent cases last up to 4 weeks per year; symptoms can range from mild (not interfering with quality of life) to moderate/severe (affecting sleep and performance).