Allergic Rhinitis Pathophysiology

What is allergic rhinitis?

inflammation of the nasal mucous membrane

What is allergic rhinitis mediated by?

IgE

When does allergic rhinitis occur?

when inhaled allergenic particles contact mucous membranes and elicit a specific response

What characteristics are associated with allergic rhinitis?

sneezing, nasal itching, watery rhinorrhea, ± nasal congestion; could also be accompanied by itching of the throat, eyes, ears, or palate

True or False: allergic rhinitis is one of the most common diseases affecting adults and children

true

What general symptoms of allergic rhinitis may affect the ability to carry out daily function?

sleep loss, general fatigue, mental fatigue, anxiety/depression, learning disabilities

What other medical conditions are associated with allergic rhinitis?

asthma, chronic rhinosinusitis, otitis media, nasal polyps, respiratory infections, orthodontic issues

What genetic factors play a role in allergic rhinitis?

risk appears to increase incrementally if 1 or 2 parents are atopic

What allergen exposures are related to the etiology of allergic rhinitis?

exposure over time to a protein that elicits the allergic response; many potential AR sufferers are unaware because they never come in contact with the allergen

What role does early microbial exposure have in allergic rhinitis?

may help prevent allergic disease by stimulating a non-atopic immune response; exposure to bacterial endotoxin seems early in life seems to have a protective effect

What other predisposing factors play a role in allergic rhintiis?

elevated serum IgE in childhood, eczema, heavy exposure to secondhand cigarette smoking

What are common indoor allergens?

house dust mite fecal proteins, cockroach fecal proteins, animal dander, mold spores

What are common outdoor allergens?

pollens (tree, grass, shrub), mold spores

What pollen is common in the spring

tree

What pollen is common in the summer

grass

What pollen is common in the fall

ragweed

What are common pollutants in allergic rhinitis?

tobacco smoke, ozone, diesel exhaust

What are common occupational irritants?

wood dust, resin, biologic enzymes, latex, organic dusts

What are the three functions of the nose to prepare incoming gases for the lung?

heats, humidifies, clean

What is the role of cilia in allergic rhintis?

cause some foreign particles to be swallowed and removed via the GI tract

Where do foreign protein material concentrate in allergic rhinitis?

the posterior nasopharynx, where lymph tissue identifies it and produce an allergic antibody response that drives allergic rhinitis

What is the immune response to the first exposure of inhaled allergens?

inhaled allergen enters the nose, allergens are processed by lymphocytes, lymphocytes produce antigen-specific IgE, sensitize the genetically predisposed host to that allergen

What is the immune response to subsequent exposure to inhaled allergens?

inhaled allergen enters the nose, allergen comes in contact with IgE bound to receptors on mast cells, mast cell degranulation and release of inflammatory mediators

What do mast cells release during degranulation of allergic rhinitis?

histamine, leukotrienes (C4/D4), kinins, prostaglandin D2, tryptase

What do the inflammatory mediators cause in allergic rhinitis?

rhinorrhea, itching, sneezing, nasal obstruction, increased nasal secretions and vasodilation

What causes itching in allergic rhintiis?

sensory nerve stimulation

What causes sneezing in allergic rhintiis?

reflex stimulation of the efferent vagal pathways

How fast does the immediate phase reaction occur in allergic rhinitis?

seconds to minutes

How long does it take for the late-phase reaction of allergic rhinitis to occur?

4-8 hours

What occurs in the late phase reaction of allergic rhinitis?

cytokines and t-helper lymphocytes → profound infiltration and activation of migrating cells → inflammatory response

What is responsible for the persistent, chronic symptoms of allergic rhinitis, including nasal congestion?

inflamed mucosa becomes hyper-responsive in the late phase reaction

What does it mean that the mucosa is hyper-responsive?

patient reacts to increasingly lower amounts of allergen; significant increases in nonspecific irritability