Influenza vs allergic rhinitis

The immune system is our inbuilt defence mechanism against things that can harm us in the outside world. Pathogens or any foreign body entering the body are usually detected by the immune system and as a result, a response is initiated to protect our body from any threat. Besides reactions to viruses or bacteria, reactions can also be initiated as a response to allergies, where individuals come into contact with a substance, known as an allergen that triggers the immune response.¹ 

What is influenza?

Influenza, or the flu, is a contagious respiratory illness caused by the influenza virus that infects the nose, throat and sometimes the lungs. This condition can cause mild to severe disease and may even lead to death in certain circumstances.²

Your body responds to the virus by creating antibodies for the specific influenza antigen to target and attack these cells.

What is allergic rhinitis?

Allergic rhinitis is when your immune response overreacts to environmental factors, such as pollen or dust and your nose is irritated or inflamed by an allergen you’re allergic to, which makes you sneeze. Allergic rhinitis is also known as hayfever and is also linked to an antibody called immunoglobulin E (IgE), which is produced by the body and is specific to certain allergens for the individual.³

Common causes include:

• Pollen from grass, trees, or weeds
• House dust mites
• Animal dander/ skin or fur
• Mould
• Wood dust, flour dust, and latex

IgE binds to receptors on mast cells found on the mucosal surfaces of the gut and lungs, in the skin and around blood vessels. Once IgE binds, signalling proteins called cytokines are triggered to release chemicals like histamine. Histamine increases the permeability of blood vessels and contraction of smooth muscles to allow more immune cells to the site for a stronger defence.

Non-allergic rhinitis is another condition, where your nose is irritated but it is not caused by any allergies but by colds, changes in the weather and even using decongestant sprays too often.. This can be confused with allergic rhinitis but it's essential to know the difference for the appropriate treatment.

Symptoms of the flu

• Fever or feeling feverish
• Chills
• Cough
• Sore throat
• Difficulty sleeping
• Loss of appetite
• Diarrhoea or stomach aches
• Feeling/being sick
• Runny or stuffy nose
• Muscle or body aches
• Headaches
• Fatigue

There is usually an incubation period, where the flu requires 1-3 days for symptoms to fully establish. A week is usually sufficient for feeling better but the fatigue can remain.⁴

Symptoms of allergic rhinitis

• Sneezing
• Itchy nose
• Runny or blocked nose
• Itchy, red and watery eyes
• Coughing
• Itchy roof of the mouth

Allergic rhinitis can be seasonal as well, depending on the allergen you’re allergic to.³

How to know if it's Influenza or allergic rhinitis?

There are key differences between the two conditions, even though they share similarities such as a cough and itchy nose or runny/stuffy nose. 

Allergic rhinitis usually flares up during seasonal changes or being around a new pet, however, the flu occurs from respiratory droplets passed on from another person, with the weather not making a difference, despite popular misconception.

The flu is also accompanied by fever and body aches, whilst allergies are not.

Are there any pre-dispositions for the flu or allergic rhinitis?

Allergic rhinitis is strongly associated with being hereditary, as changes to the genetic expression of cells that regulate the response of IgE antibodies can affect the severity of the allergic reaction and allergic rhinitis is seen to run in families. Besides environmental factors, genetic factors should also be considered.⁵

It is not fully understood whether any predetermined genetic factors make an individual susceptible to influenza.

Diagnosis

Influenza is diagnosed by a clinical evaluation to determine if the symptoms mentioned previously are present. This is further accompanied by diagnostic tests such as a reverse transcription polymerase chain reaction (RT-PCR) or rapid influenza diagnostics tests (RIDTs)⁶ to determine the specific virus strain causing the illness if needed.⁶

Allergic rhinitis requires a thorough physical examination, history evaluation and allergen skin testing for establishing an accurate diagnosis.  

A skin prick test may be requested to identify if the rhinitis is non-allergic or allergic by applying a drop of different allergen solution to different areas on your skin and then pricking your skin with a needle. Then, after 15-30 minutes they’ll inspect if there are any adverse reactions. If you are allergic to the allergen, the area affected would be irritated, red and itchy.

Intradermal testing is another testing method, where they place the allergen underneath your skin.

Lastly, an allergy blood test can be used to measure the amount of IgE antibodies produced and circulating in your blood when you come into contact with a potential allergen.^3,4 

Treatment

Allergic rhinitis

Living with allergic rhinitis can be difficult and uncomfortable but it is possible to relieve the symptoms for a short period. 

Ideally, it is best to avoid allergens if you can but if you can’t, there are methods to help ease the symptoms.

To treat allergic rhinitis, one of the methods of treatment includes using anti-inflammatory sprays to help with the swelling, such as a steroid nasal decongestant spray. By reducing the swelling the mucus in your nose will be able to flush out and your nose will no longer be blocked. Even if this is the case, you mustn't use the spray more than 2-3 times a day as your body will become dependent on the spray instead of being self-regulating. Antihistamines are also another treatment method, used to block the effects of histamine.³

Influenza

Influenza often goes away on its own but it is a good idea to rest, keep warm, keep hydrated by drinking water and take pain relief medication. Paracetamol or ibuprofen will help with treating body aches and headaches, as well as lower your temperature if you’re running a fever.

If you identify as being in the risk category for complications, it is advised to get the flu vaccine to prepare your body by producing antibodies preemptively so that when the flu strain is detected in your body there would be a stronger initial immune response.⁹ It is best to get the seasonal flu vaccine every year, as the influenza strain varies and mutates quite often, meaning that the vaccine from the year before could not be effective as it was designed for an older strain.

Complications of influenza

As catching the influenza virus is quite common when coming into contact with multiple people, some complications can ultimately turn into something fatal if not treated properly. These include bacterial pneumonia, ear infections, sinus infections and worsening chronic medical conditions like asthma, congestive heart failure or diabetes.^7,8

Complications are especially prominent in the population with compromised or weakened immune systems. These include people who are 65 years and older, pregnant women, anyone with a chronic medical condition and children younger than 5 years old.

Complications of allergic rhinitis

If allergic rhinitis is not treated this has the potential to lead to complications such as:

• Nasal polyp formation – an abnormal but non-cancerous growth inside the nose and sinuses
• Sinusitis – inflammation of the sinus that leads to blockage and mucus is therefore not able to drain through your nose
• Middle ear blockage – due to fluid build-up behind the eardrum

These conditions can be treated with medication but surgery might be required in severe cases.

Summary

In conclusion, the immune system responds differently depending on the pathogen whether it's a virus or an allergen. Allergic rhinitis is identified to be caused by both environmental factors and genetic factors but influenza is caused by the influenza virus.

In one way they are similar, as the body produces IgE antibodies for an allergic reaction and the body produces influenza-specific antibodies for influenza. However, the symptoms of both conditions are not similar beyond the runny nose or congestion and coughing. 

Treatment varies as well so it is important to know if you’re suffering from the influenza virus or an allergen to ensure you are given the appropriate medication.