Understanding the Science Behind Allergies, Antihistamine Response

March 30, 2022 - Allergies appear when the immune system reacts abnormally to a benign substance known as an allergen as if it is harmful. Allergic reactions can cause coughing, hives, sneezing, itchy eyes, rashes, a scratchy throat, and a sore throat. In severe cases, allergies can lead to trouble breathing, asthma attacks, low blood pressure, and even death. Even though allergies affect more than 50 million Americans a year, it is unclear why allergic reactions happen.

What Causes Allergies?

In the United States, allergies are the 6th leading cause of chronic illness, with an annual cost totaling more than $18 billion. Many people who experience allergies have a family history of allergies or a closely associated condition.

When an allergen triggers an allergic reaction, the immune system overreaction produces immunoglobulin E (IgE), an antibody responsible for triggering the release of histamine. Histamine is a chemical released into the bloodstream by white blood cells when the immune system detects an allergen. This chemical transmits messages in nerve cells, moves fluid through blood vessel walls, and plays a role in numerous bodily functions such as itching, inflammation, blood vessel dilation, and muscle contraction.

While most allergic reactions are harmless, a life-threatening response called anaphylaxis can occur within seconds of exposure to an allergen. Anaphylaxis produces symptoms that include rash, low pulse, shock, and sometimes death. Around 30,000 emergency room visits a year are caused by food allergy anaphylaxis. While medicines, food, and insects are the most common triggers for anaphylaxis, the Journal of Allergy and Clinical Immunology suggests that medicines cause the most allergy-related deaths.

Automatic Injection Devices and Epinephrine

Automatic injection devices (autoinjectors) help treat anaphylaxis by delivering epinephrine — the drug form of adrenaline, a powerful stress hormone and neurotransmitter produced by adrenal glands. During an allergic reaction, epinephrine relaxes blocking airway muscles and increases blood flow by tightening blood vessels. Epinephrine, also known as the fight-or-flight stress hormone, is the first line of defense in combating severe allergic reactions, including facial swelling, nausea, trouble breathing, abdominal pain, tightness of the throat, diarrhea, fainting, vomiting, and cardiac arrest.

Epinephrine binds to various receptors of cells in the body. When epinephrine binds to smooth lung muscles, the airway muscles relax, allowing a return to a regular breathing pattern. When epinephrine binds to specific receptors on immune cells, it suppresses the histamine release.

The unreasonable average price of name-brand, self-injectable epinephrine devices is a significant barrier to anaphylaxis management. Because the retail drug cost is based on the magnitude of medical benefit (value-based pricing), the product’s success and lack of competition have led to a sharp increase in the consumer price of the name-brand device EpiPen. Additionally, manufacturers suggest annual replacement of these medical devices, increasing consumer demand.

From 1987 to 2010, the average retail price of a pack of two EpiPens was less than $100. Today, name-brand and generic autoinjectors can cost over $600 and $300, respectively, without a pharmacy coupon or manufacturer’s discount. While the cost of generic epinephrine autoinjectors is covered by most insurance and Medicare plans, consumer prices may be up to 75% lower when using coupons or discounts.

What Are the Types of Common Allergies?

Common allergies include the following: drug, chemical, food, insect, latex, mold, pet, and pollen. While some allergies can be seasonal or temporary, some can be year-round and life-long. The five most common allergens are pollen, mold, food, dust mites, and bee stings.

Food Allergies

Food allergies occur when the immune system reacts with specific proteins found in food. According to the National Institute of Allergy and Infectious Diseases, approximately 5% of children and 4% of adults experience food allergies in the US. The Food Allergen Labeling and Consumer Protection Act of 2004 states that milk, eggs, fish, shellfish, nuts, wheat, and soy cause 90% of all food allergies. In the US, 200,000 people require emergency medical care annually for allergic reactions to food.

Eczema (Atopic Dermatitis)

Eczema is a chronic, non-contagious, inflammatory skin condition associated with itchy, dry skin containing clear fluid when scratched, exposing infection-susceptible wounds. According to the National Institute of Allergy and Infectious Diseases, this skin condition primarily affects children and adolescents, accounting for roughly 20% of the US population. Because people from urban regions and drier climates appear more likely to develop eczema due to decreased indoor air quality, researchers believe a combination of genetics and environmental factors may be responsible for the development of this condition. Additionally, children of parents who experience allergies and asthma are more likely to develop eczema than children of parents who don’t.

While there is no cure for eczema, some medications and treatments plans have proven successful in reducing symptoms and controlling the disease. Current patient-centered research is investigating the genetic determinants of eczema to develop new prevention strategies and treatments.

Asthma

Asthma is a chronic lung disease associated with occurrences of a narrowing airway and obstruction, leading to coughing, wheezing, chest tightness, and shortness of breath. Allergens worsen asthma symptoms, and asthma disproportionately affects minorities and families living in poverty. While asthma decreases the quality of life and can be responsible for missed time from daily activities such as work and school, severe asthma attacks can lead to emergency room visits, hospitalization, and even death.

Microbial exposure at a young age could affect the chance of developing childhood allergies and asthma; however, additional research is required to better understand the immune responses responsible for asthma — that is, genetics and environmental exposures.

Most Common Allergy Testing Method

Skin prick tests (SPTs) are among the most accurate and inexpensive ways to diagnose allergies. In SPTs, a physician places a small amount of the possible allergen on the skin and observes if a reaction occurs.

Environmental Impacts on Allergies

Environmental impacts such as climate change and botanical sexism are partly to blame for decreased air quality and longer allergy seasons. Carbon pollution caused by burning fossil fuels has increased global temperatures, which extends warm seasons and causes plants to increase pollen production. Between 1995 and 2011, warmer temperatures extended pollen seasons by 11–27 days in the US.

In 1949, the USDA Yearbook of Agriculture focusing on forests and trees recommended that only male, non-fruit-bearing trees be planted in urban regions because they are less messy than female, fruit-bearing trees, leading to a practice called botanical sexism. According to horticulturist Thomas Leo Ogren, this practice has led to uncontrollable pollen and longer-lasting allergy symptoms over the last few decades. Scientists predict that average pollen counts in 2040 will be more than double those in 2000.

Current Research and Future Potential

Because many current allergy and asthma treatments are designed to prevent or control symptoms, several researchers are devoted to decreasing the burden of this chronic disease by using growing knowledge of the underlying cellular mechanism to create targeted therapies.

Researchers from the Benaroya Research Institute at Virginia Mason in Seattle, Washington, are currently using allergy and asthma biomarkers to study the immune response responsible for allergic reactions to monitor disease progression and potentially develop allergy vaccines.