Seasonal Allergies

Introduction

Allergic rhinitis, or hay fever, occurs when individuals inhale or come into contact with typically harmless environmental allergens, perceived as threats by the immune system. Common triggers include dust mites, insect droppings, pet dander, mold spores, and various pollens. This prompts the immune system to release immunoglobulin antibodies, leading to the release of chemicals like histamine, kinins, leukotrienes, and prostaglandins into the bloodstream to combat the perceived threat. This results in symptoms akin to a common cold. Avoiding allergen exposure may not always be feasible.

In the United States, 58 million people suffer from allergic rhinitis, and 26 million experience mixed rhinitis. Allergic rhinitis typically develops in childhood for 70% of patients. Workplace productivity decreases in 36-59% of those with allergic rhinitis, and 20% report declining attendance. Among schoolchildren with seasonal allergies, 42% note reduced work efficiency and exam scores. Over 40% of the entire population experiences allergic rhinitis, with a significant increase over the past two decades.

Types of Allergic Rhinitis

Allergic rhinitis can fall under one of three categories. Mild rhinitis does not interfere with the execution of daily functions. Moderate and severe allergic rhinitis may cause difficulty executing daily functions, sleep disturbances, sinusitis, ear infections, and aggravation of asthma, and other atopic linked conditions.

Difference between Allergic Rhinitis and Common cold

A critical difference between hay fever and the common cold is that the latter is caused by a virus, rather than allergenic triggers. Seasonal allergies also present clear, liquidy, nasal discharge without a fever, and symptoms are demonstrated whenever allergic triggers are present, and will persist throughout the duration of exposure. However, the common cold yields viscous, yellow nasal discharge with a mild fever, and symptoms become evident 24-72 hours after exposure to the virus, and may take up to a week to diminish.

The sequence in which an allergic reaction is created. (Source)

Molecular underpinnings of Allergic Rhinitis

Antigenic peptides form when allergens are introduced into the nasal mucosa by antigen-presenting cells, such as basophils, eosinophils, monocytes, neutrophils, and T cells (APCs). These peptides activate simple T cells (Th0), which transform into the Th2 subclass after interaction. B cells are then stimulated to release IgE due to IL-4 production by Th2 cells. When IgE binds with mast cells and basophils, allergen exposure triggers degranulation, releasing mediator chemicals like histamine, kinins, leukotrienes, and prostaglandins into the bloodstream, causing allergic symptoms.

The process of how an allergic reaction caused by seasonal allergens is created. (Source)

Symptoms

Symptoms of seasonal allergies encompass sneezing, coughing, fatigue, nose, mouth, or throat itchiness, allergic conjunctivitis (manifested by red, itchy, watery eyes), congestion, postnasal drainage (mucus traveling through the throat), and allergic shiners (swelling beneath the eyes) when exposed to allergens. Symptoms of allergic rhinitis are immediately triggered and may persist for up to an hour after the allergen is removed. Symptoms can be categorized as early-stage or late-stage reactions, representing typical hay fever symptoms and inflammatory cells causing nasal hyperresponsiveness, respectively. Eosinophil cells produce interleukin IL-5, resulting in nasal irritation when exposed to non-allergen-related pungent odors like cleaning products and perfumes.

This graph outlines the differences between early phase and late phase reactions. (Source)

Risk factors of Allergic Rhinitis

The likelihood of developing allergic rhinitis can be exacerbated by several risk factors which include familial history or personal suffering from additional allergies, asthma, or atopic dermatitis (eczema). Furthermore, the risk of seasonal allergies is escalated by viral or bacterial infections, an imbalance in diet, prolonged contact with animals, and regular exposure to environments containing allergens, smoke, chemicals, pollution, or highly pungent odors, especially during infancy.

The genetic link of families comprising several members with allergic conditions is known as atopic, increasing the likelihood of developing an allergic condition. Over 50% of those born into an atopic family will develop an allergic disorder, while the risk for those born into a non-atopic family lies at 20%. Furthermore, the development of an allergic disease becomes increasingly probable, if both parents are carriers of the atopic genetic link. However, an atopic link does not guarantee the presence of allergies, or an identical allergic condition, in offspring, and seasonal allergies can still be present in those without an atopic link.

Testing for Allergic Rhinitis

If allergic rhinitis is suspected, skin prick testing or allergen-specific immunoglobulin serum testing, which references the medical history of the patient, can be conducted to confirm and identify allergic triggers. An allergy blood test, which measures the quantity of immunoglobulin in a sample of blood, can also be conducted.

Treatment

For those with slight or infrequent irritation from seasonal allergies, antihistamines, which can be obtained over-the-counter or through a prescription can be utilized. Antihistamines prevent the immune system from dispatching histamine to combat the allergen, essentially neutralizing allergic symptoms. Oral antihistamines can alleviate congestion, allergic conjunctivitis, and swelling, and can be consumed through a pill, tablet, or liquid. Oral antihistamines include cetirizine, desloratadine, fexofenadine, levocetirizine, and loratadine. Diphenhydramine and chlorpheniramine can also be used, however, these have a greater tendency to cause drowsiness. Prescription antihistamine nasal sprays, such as azelastine and olopatadine can help alleviate allergic symptoms. However, nasal spray antihistamines may have an unpleasant taste, and cause drowsiness. Antihistamine eyedrops, such as ketotifen and olopatadine can be prescribed or obtained over-the-counter. Antihistamine eyedrops may cause headaches and dryness in the eyes.

Decongestants can offer short-term, nearly instantaneous relief from congestion. Decongestants may cause difficulty sleeping, irritability, headaches, and a rise in blood pressure. Those with high blood pressure, glaucoma, heart conditions, and hyperthyroidism are cautioned against consuming decongestants. Oral decongestants, including pseudoephedrine, are often sold over the counter and can be taken in pill, tablet, or liquid form. Typically, oral allergy treatments are comprised of both a decongestant and an antihistamine. Nasal decongestant sprays, such as oxymetazoline and tetrahydrozoline, can be beneficial in limited quantities. However, nasal decongestants may worsen symptoms after extended use or improper dosage.

This table further breaks down conventional treatment methods.

Mast cell stabilizers are similar to antihistamines, as they also prevent the immune system from dispatching chemicals, such as histamines, which result in allergic symptoms. However, they are used for more serious allergic rhinitis cases, when antihistamines do not suffice. Mast cell stabilizers are not used as a primary resort, as they pose a minor risk factor, and require several days of use to render maximum usefulness. Mast cell stabilizers can be obtained as over-the-counter nasal sprays such as cromolyn, or prescribed eye drops such as cromolyn, lodoxamide, and nedocromil.

Leukotriene inhibitors are oral medications obtained through a prescription, and operate similarly to antihistamines, yet rather than preventing the delivery of histamines, prevent the release of leukotrienes. Therefore, allergic symptoms including congestion and sneezing are alleviated. Currently, montelukast is the only approved leukotriene inhibitor for seasonal allergies. However, leukotriene inhibitors are known to potentially cause adverse psychological effects including anxiety, depression, and various sleep disturbances.

Immunotherapy is designed to build up a gradual tolerance for and eventually the absence of a reaction by the immune system to unavoidable environmental allergens, and is used when antihistamines are unsuccessful. Immunotherapy exposes the patient to mild versions of an allergen, initially provoking allergic reactions, which will diminish over time. Immunotherapy can be administered through injections, with a gradual increase in dosage over the course of several weeks. Sublingual immunotherapy requires the patient to ingest a tablet, such as odactra, ragwitek, oralair, and grastek, infused with one or multiple allergens to encourage tolerance. Biological medications are injections designed to focus on a singular reaction from the immune system and ensure that it cannot be executed, therefore preventing allergic symptoms. Dermal reactions are addressed by dupilumab, and hives are addressed by omalizumab. Biological medications may cause irritation and redness at the area of the injection.

This table further breaks down unconventional treatment methods.

References

1. "Allergy Medications: Know Your Options." Mayo Clinic, www.mayoclinic.org/diseases-conditions/allergies/in-depth/allergy-medications/art-20047403 . Accessed 3 Aug. 2023.

2. Beard, Sheryl. "Rhinitis." Science Direct, www.sciencedirect.com/science/article/pii/S0095454313001012?via%3Dihub. Accessed 2 Aug. 2023.

3. Drazdauskaitė, Gabija et al. "Mechanisms of Allergen Immunotherapy in Allergic Rhinitis." Current allergy and asthma reports vol. 21,1 2. 12 Dec. 2020, https://pubmed.ncbi.nlm.nih.gov/33313967/ doi:10.1007/s11882-020-00977-7

4. "Hay Fever." Mayo Clinic, www.mayoclinic.org/diseases-conditions/hay-fever/symptoms-causes/syc-20373039. Accessed 28 July 2023.

5. "Let's Talk about Seasonal Allergies." 23 and Me, www.23andme.com/topics/wellness/seasonal-allergies/. Accessed 26 July 2023.

6. Modi, Juhi. "Are Seasonal Allergies Genetic?" Edited by Andres Maldonado. BuzzRx, 1 May 2023, www.buzzrx.com/blog/are-seasonal-allergies-genetic. Accessed 26 July 2023.

7. Smith, Yolanda. "Allergies and Genetics." Edited by Benedette Cuffari. News Medical Life Sciences, www.news-medical.net/health/Allergies-and-Genetics.aspx . Accessed 1 Aug. 2023.

8. Wang, De-Yun. "Risk factors of allergic rhinitis: genetic or environmental?." Therapeutics and clinical risk management vol. 1,2 (2005): 115-23. https://pubmed.ncbi.nlm.nih.gov/18360551/ doi:10.2147/tcrm.1.2.115.62907

9. Wermuth, Harrison R., et al. "Montelukast." StatPearls, StatPearls Publishing, 22 March 2023.

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_By: Nishka Patankar_

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of Elio Academy.