What Is Inhaled Allergens?

  • Linda NkrumahBiological Sciences with International Year, University of Birmingham, UK


Inhaled allergens are substances in the environment that, when inhaled, can trigger allergic reactions in individuals who are sensitive to them. These allergens are typically harmless to most people but can cause a range of symptoms and health issues in those with allergies. Common inhaled allergens include pollen, dust mites, pet dander, and mould spores. Understanding these allergens and their effects is so important for people who are more susceptible to reacting.  

Allergies are on the rise worldwide, affecting millions of people. Inhaled allergens play a significant role in causing allergic reactions, which can be uncomfortable and, in some cases, life-threatening. 

In this article, we will delve into the various types of inhaled allergens, how they trigger allergic reactions, common allergic conditions associated with them, methods of diagnosis, and strategies for prevention and management. 

Types of inhaled allergens 


Pollen allergies, often referred to as hay fever or allergic rhinitis, are highly seasonal. Pollen is a common inhaled allergen produced by plants for reproduction. Trees, grasses, and weeds release pollen grains into the air, where they can be inhaled by individuals with allergies. Different types of plants release pollen at different times of the year, leading to varying symptoms in spring, summer, and fall. 

Dust mites 

Dust mites are microscopic insect-like pests that thrive in household dust. They feed on dead skin cells and are commonly found in bedding, carpets, and upholstered furniture. When their faeces and body fragments become airborne, it can trigger a reaction in those who are allergic.

Pet dander 

Pet dander consists of tiny particles of skin flakes, saliva, and urine from cats, dogs, and other animals with fur or feathers. 

Pet dander can create an allergic reaction in individuals who are sensitive to it. Symptoms may vary from mild to severe and can be particularly challenging for pet owners with allergies. 

Mould spores 

Mould spores thrive in damp and humid environments. They can be found both indoors and outdoors and often grow in places with a lot of moisture, such as around leaks in roofs or windows or where there has been flooding.

Inhaling mould spores can lead to various health issues, including allergic reactions, respiratory problems, and fungal infections. Individuals with compromised immune systems are particularly vulnerable. 

How inhaled allergens trigger allergic reactions 

Immune system response 

When inhaled allergens enter the body, the immune system recognises them as foreign invaders and produces antibodies (the proteins in your body that protect you from bacteria and viruses). Allergic reactions specifically trigger an antibody called immunoglobulin E (IgE).1 

Histamine release 

The IgE antibodies are triggered when you are first exposed to an allergen release of histamine and other chemicals. Histamine is responsible for many allergy symptoms, such as sneezing, itching, and congestion. 

Symptoms of allergic reactions 

Respiratory symptoms 

  • Sneezing: Frequent and repetitive sneezing is a common allergic response, especially when exposed to inhaled allergens like pollen or dust mites.
  • Nasal congestion: Allergens can cause the nasal passages to become congested, making it difficult to breathe through the nose.
  • Runny nose: An increase in nasal discharge is a typical allergic symptom, often accompanied by clear or watery mucus.
  • Coughing: Allergies can irritate the throat and airways, leading to bouts of coughing.
  • Wheezing: Wheezing is a whistling or rattling sound that can occur when the airways constrict due to exposure to allergens, particularly in individuals with asthma.
  • Shortness of breath: In some cases, allergic reactions can lead to difficulty breathing or a sensation of breathlessness.
  • Chest tightness: Allergic reactions may cause chest discomfort or tightness, especially in individuals with asthma.2

Skin reactions 

  • Itching: One of the most common skin symptoms associated with allergies is itching, which can affect different parts of the body.
  • Hives: Hives, also known as urticaria, are raised, itchy welts on the skin that can vary in size and shape.
  • Eczema flare-ups: Allergic reactions can exacerbate existing atopic dermatitis (eczema), leading to redness, inflammation, and increased itching.
  • Contact dermatitis: Inhaled allergens can sometimes cause contact dermatitis, a skin rash triggered by direct skin contact with the allergen.

Eye and nasal symptoms 

  • Red, itchy eyes: Allergies can cause the eyes to become red, itchy, and irritated.
  • Watery eyes: Increased tear production is a common response to eye irritation caused by allergens.
  • Runny nose: In addition to nasal congestion, allergies often result in a runny or drippy nose.
  • Postnasal drip: Allergens can trigger excess mucus production, leading to the sensation of mucus dripping down the back of the throat.

Common allergic conditions related to inhaled allergens 

Allergic rhinitis (Hay fever) 


Allergic rhinitis, commonly known as hayfever, is characterised by symptoms such as sneezing, nasal congestion, runny nose, itchy or watery eyes, and fatigue. These symptoms can be bothersome and affect daily life.

Seasonal vs. perennial allergic rhinitis 

Seasonal allergic rhinitis occurs during specific times of the year, usually when certain plants release pollen. Common triggers include tree pollen in spring, grass pollen in late spring and summer, and weed pollen in late summer and fall.   

Perennial allergic rhinitis, on the other hand, can occur year-round due to indoor allergens like dust mites and pet dander.3 Symptoms, therefore, persist regardless of the season. 


Relationship with inhaled allergens 

Inhaled allergens are a significant trigger for asthma. Exposure to allergens can lead to asthma symptoms such as coughing, wheezing, shortness of breath, and chest tightness. 

Triggers and symptoms 

Asthma exacerbations can be triggered by inhaled allergens, tobacco smoke, pollution, respiratory infections, and exercise. Managing allergen exposure is crucial for asthma control. 

Atopic dermatitis (Eczema) 

Skin allergies and inhaled allergens 

While atopic dermatitis is primarily a skin condition, inhaled allergens like pollen can exacerbate symptoms. Allergic reactions can lead to skin flare-ups characterised by red, itchy, and inflamed patches. 

Effects on skin health 

Inhaled allergens can compromise the skin's barrier function, making it more susceptible to irritants and infections. Proper management of inhaled allergens is essential for maintaining healthy skin in individuals with eczema. 

Diagnosis of inhaled allergies 

Allergy testing 

Skin prick test 

Skin prick tests involve applying small amounts of allergen extracts to the skin's surface and then pricking or scratching the skin to introduce the allergen.4 A positive reaction indicates that the body is more sensitive to that allergen.  

Blood tests (RAST) 

Blood tests, such as radioallergosorbent testing (RAST) or specific IgE tests, measure the levels of allergen-specific antibodies (IgE) in the blood. Elevated IgE levels to specific allergens indicate a sensitivity or allergy. 

Importance of identifying specific allergens 

Identifying the specific inhaled allergens responsible for an individual's symptoms is crucial for developing an effective allergy management plan. It allows for targeted allergen avoidance and, if necessary, the initiation of allergen-specific treatment (such as immunotherapy).   

Prevention and management 

Allergen avoidance 

Home environment 

  • Dust Mites 
    • Use allergen-impermeable covers on pillows and mattresses 
    • Wash bedding in hot water regularly 
    • Maintain low humidity levels 
  • Pet Dander 
    • Keep pets out of bedrooms 
    • Bathe and groom pets regularly 
    • Use HEPA air purifiers 
  • Mould 
    • Keep an eye out for any water leaks and dampness and ensure they are fixed quickly 
    • Use dehumidifiers 
    • Ensure proper ventilation, especially in bathrooms and basements 

Outdoor precautions 

  • Pollen 
    • Stay indoors on high-pollen days 
    • Keep windows closed 
    • Use air conditioning with clean filters 
  • Mould 
    • Avoid outdoor activities in damp or rainy conditions 



Antihistamines are commonly used to relieve allergy symptoms. They work by blocking histamine receptors and reducing itching, sneezing, and congestion.  

Some people with allergies take antihistamines regularly, especially during allergy seasons or when they anticipate exposure to known allergens. This can help prevent the onset of symptoms or reduce their severity if exposure occurs. 

It is essential to note that some antihistamines cause drowsiness as a side effect, whereas others do not. Make sure you read the instructions carefully before taking any medication, as this can be dangerous if driving or working heavy machinery. 


Decongestants help alleviate nasal congestion by narrowing blood vessels in the nasal passages, which reduces the swelling and congestion that can come from allergic reactions. Decongestants are known for providing quick relief from congestion by helping people breathe more easily when congested. The duration of decongestants’ effects varies, but generally, over-the-counter forms last a few hours. It is important to note that taking too much or taking them for too long can lead to a condition called "rebound congestion" where symptoms worsen with continued use. 


Immunotherapy involves regular injections of allergen extracts to desensitise the immune system (allergy shots).5 The way that this works is by exposing the body to small amounts of the allergen, which should cause a reaction but not enough to cause physical symptoms, to build a ‘tolerance’ of sorts. Over time, this can reduce allergic reactions and improve allergy symptoms. It is typically recommended for individuals with severe allergies who do not respond well to other treatments. 


Inhaled allergens, including pollen, dust mites, pet dander, and mould spores, are common inhaled triggers of allergic reactions. These allergens can cause several uncomfortable symptoms, which can have a large impact on daily life. 

Living with allergies can be challenging, but with proper understanding and management, individuals can lead healthy, fulfilling lives. Allergen avoidance, medication, and immunotherapy can provide relief, allowing individuals to enjoy a better quality of life. Remember, you are not alone, and there are resources and treatments available to help you manage your allergies effectively. 


  1. Ansotegui IJ, Melioli G, Canonica GW, Caraballo L, Villa E, Ebisawa M, et al. IgE allergy diagnostics and other relevant tests in allergy, a World Allergy Organization position paper. World Allergy Organization Journal [Internet]. 2020 Feb [cited 2023 Sep 11];13(2):100080. Available from: https://linkinghub.elsevier.com/retrieve/pii/S1939455119312360 
  2. Dougherty JM, Alsayouri K, Sadowski A. Allergy. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 [cited 2023 Sep 11]. Available from: http://www.ncbi.nlm.nih.gov/books/NBK545237/ 
  3. Mackay IS, Durham SR. ABC of allergies: Perennial rhinitis. BMJ [Internet]. 1998 Mar 21 [cited 2023 Sep 11];316(7135):917–917. Available from: https://www.bmj.com/lookup/doi/10.1136/bmj.316.7135.917 
  4. Muthupalaniappen L, Jamil A. Prick, patch or blood test? A simple guide to allergy testing. Malays Fam Physician [Internet]. 2021 Jul 22 [cited 2023 Sep 11];16(2):19–26. Available from: https://e-mfp.org/wp-content/uploads/v16n2-RV-Prick-patch-or-blood-test_.pdf 
  5. Pavón-Romero GF, Parra-Vargas MI, Ramírez-Jiménez F, Melgoza-Ruiz E, Serrano-Pérez NH, Teran LM. Allergen immunotherapy: current and future trends. Cells [Internet]. 2022 Jan 8 [cited 2023 Sep 11];11(2):212. Available from: https://www.mdpi.com/2073-4409/11/2/212
This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Chavini Ranasinghe

Bachelor of Medicine, Bachelors of Surgery - MBBS, University College London

Bachelor of Science in Global Health - BSc (Hons), University College London

Chavini is a junior doctor currently working within the NHS. She also has several years of experience within medical education and has published multiple scientific papers on a wide range of topics. Her exposure to clinical practice and academia has helped her to develop an interest in sharing accessible and accurate medical information to the public.

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