Links To And Excerpts From Dust Mite Allergy From StatPearls-Part 1

In this post, Part 1, I link to and excerpt from Dust Mite Allergy from Treasure Island (FL)  StatPearls Publishing; Last Update: August 16, 2020. This post covers the evaluation of dust mite allergy.

For treatment, please see my post, Links To And Excerpts From Dust Mite Allergy From StatPearls-Part 2, in which I review the treatment of dust mite allergy from Dust Mite Allergy from Treasure Island (FL)  StatPearls Publishing; Last Update: August 16, 2020.

Here are excerpts:

Introduction

Dust mite allergy is an allergic condition that occurs as a reaction to the dust mite allergens that commonly live in household dust. It is also known as house dust allergy. It is sensitization and an allergic reaction to the droppings of the dust mites. The droppings are an indoor aeroallergen, which on inhalation triggers the allergic reaction. The prevalence of atopic diseases like allergic rhinitis and asthma with house dust mite being the allergen has been increasing.

The house dust mite (HDM or DM) is a predominant source of indoor aeroallergens. Some of the allergic diseases that have been associated with the HDM are allergic rhinoconjunctivitis, allergic asthma, and atopic eczema. The best treatment strategy for allergic rhinitis consists of allergen avoidance first, in junction with pharmacotherapy and allergen immunotherapy (AIT).[2] The appropriate pharmacotherapy consists of antihistamines, leukotriene receptor antagonists, and inhaled or intranasal corticosteroids (ICS). All these treatments are effective and safe, but unfortunately, haven’t proved to change the course of HDM related allergic diseases.

Epidemiology

Dust mite allergy is a prevalent form of allergy. It affects 20 million people across The United States of America.

Up to two-thirds of children with asthma and up to 1/2 of adults who have asthma also suffer from allergies. Of these patients who suffer from asthma and allergies, about 40%-85% of them are allergic to the HDM, this trend is observed all over America, Europe, south-east Asia, and Australia. Around 5 to 30 percent of the general population show house dust mite sensitivity to skin test reactivity.

Pathophysiology

IgE mediated sensitization is responsible for the pathogenesis of dust mite allergy. This a Type 1 hypersensitivity reaction in which the CD4 + and T helper cells stimulate the B cells to produce IgE antibodies specific to the antigen, which is the house dust mite allergen.

Asthma usually develops as a result of combined environmental and genetic factors. Dust mite allergy leads to the development of atopic asthma, which is a predisposition to the development of hypersensitivity Type 1 reactions.

House dust mite allergy plays a role in the development or exacerbation of atopic dermatitis.

History And Physical Exam

Dust mite allergy leads to perennial allergic rhinitis; that is, the symptoms of dust mite allergies occur throughout the year. Symptoms are more likely to occur while sleeping at night and early in the morning on waking up because the dust mites inhabit the pillows, bedcovers, mattresses, and blankets. Common dust mite allergy symptoms include:

• Sneezing
• Rhinorrhea
• Allergic conjunctivitis
• Nasal stuffiness
• Itchy nose, mouth or throat
• Itchy skin
• Postnasal drip
• Cough
• Coughing bouts that may be exacerbated by a viral infection
• Lethargy, malaise
• Impaired sleep caused by shortness of breath, coughing or wheezing

If dust mite allergy triggers asthma, the following may also present:

• Dyspnea
• Chest tightness or discomfort
• Wheezing on exhalation

The following risk factors predispose an individual to develop dust mite allergy:

• Childhood or adolescence
• Family history of allergies
• Exposure to a high level of dust mites

The development of allergies to certain foods like shellfish or mollusks can also occur as a result of cross-reactivity.

Evaluation

In vivo techniques

• Skin prick test. It has high sensitivity and is preferred as the first-line test for the detection of sensitization of dust mite allergy. It is a convenient, inexpensive test that yields results within 20 minutes. However, it may produce a high number of false-positive results owing to cross-reactivity. It is not indicated in people with dermatitis or those using antihistamines.
• Atopic patch tests. It detects the T cell-mediated reaction in the allergy.[18]
• Basophil activation test (BAT). It is a quantitative test that detects the activation markers on the basophil surface in whole blood. This test can be performed in patients who are already taking antihistamines. It also demonstrates a functional response. However, inconsistent results may be present because of the different varieties of commercial testing kits and varied protocols used.[19]
• Nasal provocation test. It identifies and quantifies the clinical relevance of dust mite allergen. The respiratory mucosa is exposed to the dust mite allergen, and the consequent clinical reactions are monitored. Anterior rhinomanometry and acoustic rhinometry are then used for the graphical display of the changes in nasal airflow and patency.[20]
• IgE blood test

In vitro techniques

• Enzyme-linked immunosorbent assay (ELISA). It can detect both total and selective IgE levels. Taking cross-reactivity of IgE into consideration, competitive ELISA can be used. The disadvantage is that ELISA cannot be used for a thorough analysis of multiple allergens.
• Radio allergen sorbent test (RAST). It is an in vitro test for the detection of IgE levels. The serum IgE of the patient bound to the allergen is immobilized on a solid substrate, and then these are detected using radiolabelled anti-IgE antibodies. Its use has become limited due to the availability of better techniques like ELISA.[21]
• Microarrays. It can be used to detect multiple antigens on a single slide. It includes single-plex (ImmunoCAP) and multiplex (ImmunoCAP ISAC) assays. One commercially available microarray is ImmunoCAP immunosorbent allergen chip (ISAC) that is used to define an individual’s complete allergen sensitivity profile. A better available microarray is a MeDALL chip that can be used to monitor IgE and IgG reactivity profiles toward more than 170 allergens, but this is still under evaluation. These assays are expensive and available in large hospitals, thus cannot be used to detect dust mite allergy sensitization at the primary point of care.[22]
• Fluoroenzyme immunoassays

Diagnosis of asthma. Over time dust mite allergy culminates into asthma or may lead to exacerbation of asthma.

• Peak expiratory flow rate (PEFR). In mild asthma, PEFR is more than or equal to 200 L per minute, with moderate asthma, PEFR is 80 to 200 L per minute, in severe asthma PEFR is less than 80 L per minute.
• Spirometry. The methacholine challenge test is used when there is no acute asthma. A fall of FEV1 of less than 20 percent after administering methacholine is diagnostic for asthma. During acute asthma, inhaled beta-agonists like salbutamol can be administered. A rise of FEV1 by 12 percent or more is diagnostic of asthma. Asthmatics sensitized to house dust mites have lower FEV1/FVC ratio as compared to asthmatics without the sensitization.[23]

For treatment, please see my post, Links To And Excerpts From Dust Mite Allergy From StatPearls-Part 2, in which I review the treatment of dust mite allergy from Dust Mite Allergy from Treasure Island (FL)  StatPearls Publishing; Last Update: August 16, 2020.