What Role Do Allergies Play In Rsv Susceptibility?

Overview

Respiratory syncytial virus, often referred to as RSV, is a common virus affecting the respiratory organs, such as the lungs. RSV primarily affects children under the age of five, causing 33,500 hospitalisations, and 20 to 30 deaths within this age group each year in the UK.¹ This infection often causes mild, cold-like symptoms, which, when left untreated, or when individuals with underlying conditions(resulting in a compromised immune system become infected, can manifest into bronchiolitis and other more serious complications. 

An allergy is an example of an underlying condition associated with increased susceptibility to RSV. Allergies are hypersensitive immune responses to specific non-damaging triggers, including foods, fur, pollen, and dust, which can be damaging to the sufferer.²

This article will explore RSV and its relationship with allergies, aiming to highlight the link between the two conditions and methods taken to reduce RSV susceptibility in those with allergies.

Understanding RSV

Defining RSV infections

RSV is a contagious virus, passed from person to person through droplets in an infected person’s cough or sneeze. RSV can be caught directly from the release of the droplets, or indirectly through touching surfaces contaminated with the droplets and transferring them to the face (by itching or rubbing). 

Symptoms

Symptoms of RSV can be mild or severe:³

• Mild: Runny nose, coughing, sneezing, fever, and wheezing
• Severe: Inflammation of the small airways in the lung (bronchiolitis), pneumonia, difficulty breathing, hyperventilation (rapid breaths), and blue-ish skin (cyanosis)

Risk factors

The groups most vulnerable to developing RSV are babies born prematurely (before their due date), children under the age of two with chronic lung disease or congenital heart disease, anyone with a weakened immune system, older adults, and older adults with either chronic lung or heart disease.^1,3

Diagnosis

RSV is easily diagnosed by doctors using clinical symptoms and the medical history of a patient. However, various diagnostic laboratory tests can be carried out on blood samples to confirm the presence of the exact virus to ensure a correct diagnosis. Chest X-rays may also be appropriate for older patients to diagnose RSV based on lung inflammation.¹

Allergies and the immune response

Basics of allergies and allergic reactions

The body can mistakenly recognise harmless things (known as allergens), such as certain foods, dust, and pollen, as threats, resulting in an overreaction of the immune system known as an allergy. An allergy is often recognisable by sneezing, runny eyes and nose, itching, and rashes. In extreme cases, most commonly seen in nut allergies, more severe symptoms such as difficulty breathing and life-threatening shock (anaphylaxis) can occur. Allergies are common conditions in all age groups and genders, affecting 1 in 4 people in the UK; however, the severity of the allergy changes from person to person.¹

How allergies affect the immune system

When the body is first exposed to something it considers a threat, regardless of whether it actually is a threat or not, an antibody is produced. Think of an antibody as the body’s key to stopping and killing threats. In allergies, IgE antibodies are produced, which are specialised to communicate with histamine-releasing immune cells (mast cells and basophils).⁴ Histamine is a chemical released by the body which causes the muscles of the tubes (bronchioles) going into the lungs to tighten, resulting in distinctive allergy symptoms such as sneezing and a runny nose.⁵ The immune system does not mean to cause harm or illness, its goal is to prevent these things. Repeat exposure to the allergen(s) over time can result in worsening and more severe symptoms, so it is important to avoid the allergen(s) in day-to-day life. 

The link between allergies and RSV susceptibility 

Research findings linking allergies and RSV susceptibility

Research has found that people with allergies, especially children, are more likely to get severe RSV infections due to their immune systems being on high alert, making their airways more susceptible to infections. A 2007 study by  Ohio State University showed that allergies can cause inflammation in the airways, which makes it easier for RSV infections to occur, become more frequent, and become more severe.⁶ 

Mechanisms proposed for increased susceptibility 

Allergies cause damage to the lining of the airways, often leading to inflammation. Damage to the airways makes it easier for RSV to penetrate and cause an infection. Additionally, the extra mucus produced by allergies can trap RSV in the airways and aid its spread. RSV replication is aided further by increased immune cell recruitment caused by the allergy. Allergies also weaken the body's natural defences against viruses, making it easier for RSV to thrive. This combination of factors means that people with allergies are more likely to get infected with RSV and have more severe symptoms.⁷

Clinical implications 

The increased susceptibility to RSV in allergic individuals, especially children with conditions such as asthma, imposes a higher risk for severe RSV infections, which can lead to hospitalisation and increased mortality.¹ Effective management and treatment of allergic conditions, and the RSV infection if developed, can help reduce risks of severe complications. 

Management and treatment of allergies 

Allergies can be managed by:²

• Monitoring and keeping note of where and when a reaction occurs, helping to pinpoint its cause
• Once the allergen is identified, the allergen can be avoided, where possible, to reduce the risk of a reaction
  
  Medications can be prescribed including, but not limited to:
  
• Antihistamines to reduce the histamine release preventing or mitigating symptoms
• Decongestants to relieve a blocked nose, such as nasal sprays
• Lotions and creams to relieve skin rashes and redness, such as emollients; and
• Steroid medications to relieve allergy-mediated redness and swelling, such as inhalers and sprays

Management and treatment of RSV

RSV infections can be managed by:³

• Staying hydrated, as dehydration can exacerbate symptoms
• No smoking, or no smoking around an infected individual, to prevent further aggravation of the airways
• Administering a recommended dose of paracetamol or ibuprofen to relieve fever symptoms. Aspirin may be appropriate for older adults, but should not be given to a child under the age of 16
• Saline nasal drops can relieve nasal blockages without a prescription

Summary

RSV is a common respiratory virus largely affecting children under five, potentially leading to hospitalisations and deaths. While RSV often causes mild, cold-like symptoms, it can develop into more complicated and serious illnesses such as bronchiolitis. Allergies, caused by hypersensitive immune responses to non-damaging allergens, are linked to increased RSV susceptibility. Allergic reactions involve the production of IgE antibodies by the immune system, leading to histamine release. Since there is no threat, histamine causes unnecessary inflammation in the airways and causes a negative response, presenting as cold-like symptoms. This inflammation, combined with excess mucus, creates an environment where RSV can flourish and cause more rampant infection. Research highlights that individuals affected by allergies face a higher risk of severe RSV infections due to their compromised airway defences. Effective management of allergies and RSV includes avoiding known allergens, using medications like antihistamines and decongestants, and ensuring hydration and proper symptom relief for RSV. These approaches can help prevent the severe complications associated with RSV in allergic individuals.