Can air purifiers help with allergies?

This article discusses how air purifiers help with allergies. We first discuss the potential allergens present in the indoor air, and how air purifiers can counteract those.

Can air purifiers help with allergies?

Yes, air purifiers help with allergies. Air purifiers are devices which, as the name suggests, help to clean the indoor air. There are various types of air purifiers available, but the most suitable against indoor allergens are air purifiers with HEPA filters.

HEPA stands for High Efficiency Particulate Air. Air purifiers with HEPA filters pull in the ambient indoor air and pass  it through the filter. The various pollutants present in the air get stuck on the filter, thereby giving out clean air.

These air purifying devices usually come with additional components, such as UV light chamber, activated carbon filter, ionisers, etc., which help to increase the air purifying devices’ efficacy against various forms of allergens.

Various allergens in the indoor environment

There are mainly two forms in which allergens exist – either as particulate matter (PM), or as gases. We shall discuss each one of these classes, and the common types of allergens among them.

Particulate matter (PM)

Particulate Matter, or simply PM, refers to particles in the sub-micron range that are suspended in the air. 

There are two forms of particulate matter: coarse particulate matter (PM10) and tiny particulate matter (PM2.5). PM2.5 is a prevalent problem among them.

There are many sources of PM in the ambient air. Some of the main sources include factories, power plants, refuse incinerators, fumes from automobiles, construction activities, fires and natural windblown dust.

Indoor sources include burning of  fuels, smoking, and other hobbies, such as woodworking, painting, etc.

Numerous studies have shown that exposure to polluted air containing particulate matter have been shown to cause various issues, such as:

  • premature death in people with heart or lung disease
  • nonfatal heart attacks
  • irregular heartbeat
  • aggravated asthma
  • decreased lung function
  • increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing.

Given the variety of PM present, they have various sources. These particles can originate from a variety of sources, which can be indoors, or outdoor pollution that enters through doors, windows, seeps, cracks, and so on.

In an indoor environment, there are various types of PM allergens present. Some of these are:

  • Animal dander
  • Dust and dust mites
  • Insects and insect droppings
  • Mold spores and pollen
  • Smoke

Let us discuss these in more detail.

Animal dander

The dead skin flakes that dogs and cats produce on a regular basis are known as pet dander. Their saliva, urine, and faeces, can also generate allergies. Sneezing, runny nose, asthma-like wheeze, and trouble breathing are all signs of pet allergies. 

Allergy patients may also experience face pressure and pain, as well as frequent nocturnal awakenings and swollen, blue-colored skin beneath their eyes. Inflammation of the skin can result in raised red areas, eczema, and itchy skin.

Even for people who don’t own pets, animal dander can still exist, which can arise from animals from rodents such as hamsters, guinea pigs, mice, etc.

Furthermore, pet owning people that are visiting your house can also bring animal dander with them, since they can cling onto clothes and skin.

Dust and dust mites

Dust is a collective term that refers to the fine sized solid particles which arise from various sources. Most of the dust usually aggregates from outdoor sources, especially in large cities and houses near major roads.

Dust mites are tiny pests that live in humid settings and flourish. Even if your home isn’t excessively hot or humid, dust mites are likely to be lurking in your beds, carpets, and curtains.

The more dust you have, the more dust mites you have, because dust contains things like pet dander and dead skin, which are two of dust mites’ favourite diets.

Dust mites and their waste products are relatively weightless. Therefore, they can stay suspended in the indoor air for a long time, and affect one’s health if inhaled.

Insects and insect droppings

No matter how spotless one tries to keep their home, there are always certain insects lurking around in the corner. Dust mites are also one of them, and we have already discussed their contribution to indoor dust in great detail.

However, there are other types of insects, such as flies, bugs, and one of the most notorious, cockroaches. Cockroaches can easily infest homes, and hide in some of the most obscure places in the house.

Cockroaches can also trigger allergic reactions in some individuals, and their droppings can further aggravate those allergies.

Moreover, cockroaches can easily enter the household from multiple areas, so it is almost impossible to get rid of them, especially for people living in apartment complexes.

Therefore, it would be better to get an air purifier, which would help to remove dust particles associated with insects, which are suspended in the air, to prevent triggering of allergies in individuals.

Mold spores and pollen

Mold are fungal species that grow favourably under conditions such as presence of organic material, high humidity, low sunlight, and low temperatures.

These conditions are found in certain areas of the house, such as basements, bathrooms, cupboards, air conditioners, and so on.

The spores generated from mold can act as serious allergens, as they impede the optimal functioning of the respiratory system.

Pollen are tiny particles that are produced by flowering plants that help them to reproduce and give rise to seeds. One of the most common way of pollination (i.e., the act of releasing pollen), is by releasing it in the wind.

However, given their tiny size, they cause irritation in the upper respiratory system and trigger allergic reactions such as itchiness, wheezing, and asthma.

In the spring season, the amount of pollen produced is very high, which can cause ‘hay fever’, which is characterised by cold-like signs and symptoms, such as a runny nose, itchy eyes, congestion, sneezing and sinus pressure.


Smoke is one of the worst allergens, in both outdoor air as well as indoor air. It is generated by combustion of fuels such as gasoline, firewood, coal, dried dung, and from other sources such as cigarettes.

Various studies have shown how exposure to smoke can adversely affect human health, and can even cause illnesses related to the cardiovascular and respiratory system.

Smoke particularly affects certain groups of individuals, such as children and older people, people that use solid fuels for their energy needs, and so on. In children, there are higher reported cases of hospitalisation due to allergies and illnesses caused from exposure to smoke. 

Furthermore, it was also shown that respiratory illnesses such as asthma, emphysema, COPD, etc., were reported in much higher numbers for smokers, secondhand smokers, and people subjected to combustion-based pollution.


Certain indoor gaseous species can also trigger allergic reactions. These include:

  • Volatile Organic Compounds (VOCs)
  • Ozone (O3)
  • Nitrogen dioxide (NO2)

Amongst these, ozone and nitrogen dioxide are mainly outdoor pollutants that are generated by traffic-related activities. These gases are eliminated from the indoor air by using activated carbon filters. Let us discuss them in more detail.

Volatile Organic Compounds (VOCs)

VOCs refer to a variety of organic compounds that are emitted from certain materials in the form of a gas. These compounds are present in items commonly stored in houses, such as paints, solvents, cleaning products, cosmetics, and fuels. 

All of these products release VOCs when in use, as well as when they are stored. Short term exposure to VOCs can cause allergic reactions such as irritation of the eyes, nose and throat, headaches, and nausea.

Ozone (O3)

Ozone is a gaseous molecule which is naturally present in the higher layers of the atmosphere, where it absorbs the harmful UV rays of the sun. However, when present in the lower atmosphere layers, it acts as a pollutant, and can cause allergic asthma.

Ozone has a characteristic pungent odor, which can irritate the inner linings of the airways, as well as the lungs. It can hamper one’s ability to breathe deeply, and reduce lung function.

Ozone formation in the lower atmosphere is due to interaction of sunlight with fumes emitted from vehicles, which contain hydrocarbons and nitrogen oxides (NOx). 

It is a major component of “Los Angeles Smog”, or summertime smog, which occurs during summer in metropolitan cities. Studies show that cities in which LA smog occurs have a higher number of reported cases of asthma patients.

Nitrogen dioxide (NO2)

Nitrogen dioxide is a gaseous substance which originates primarily from anthropogenic activities such as vehicular exhausts, emission from industrial chimneys, and combustion of firewood.

Higher concentrations of NO2 are usually associated  with  more  frequent  asthma  symptoms  and  asthma-related problems.

Previous studies have shown a link between exposure to local traffic-related pollution to onset of asthma in children. A study estimated that an increase in NO2 concentration by 20.4 ppb (parts per billion) was associated with a 67% increase in the risk of asthma-related school absence.

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Air purifiers help with allergens. Purifiers usually utilise 2 types of filters – a HEPA filter for PM pollution, and an activated carbon filter for filtering out the gaseous allergens present in the indoor environment.

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Can air purifiers help with asthma?

Yes, air purifiers can help with asthma. Exposure to elevated concentrations of PM and certain gaseous species can trigger asthma attacks in certain people. However, air purifiers get rid of those pollutants, making the air safe to breathe.

Can we keep an air purifier on at all times?

Yes, you should keep your air purifier on at all times. This is because the pollution is more or less continuous in nature, meaning that as long as a source is present, so is air pollution, including dust.

If you turn off your air purifier, the dust particles start aggregating in the indoor air once again, which would eventually affect the health of the occupants adversely.

Furthermore, air purifiers do not consume a lot of electricity for operation, therefore making it feasible to be kept on at all times.

Where should I place my air purifier?

Ideally, you should place your air purifier in a location where the highest rate of air exchange takes place. Air exchange refers to mixing of two different types of air, which in this case refers to indoor air and outdoor air, and from one room to another.

This is because most of the pollution inside the house comes from outdoor sources. This in turn could spread to other rooms of the house. Hence, by placing an air purifier here, spread of pollutants within the house gets hampered.

Furthermore, the ideal place to keep an air purifier is to mount it on a wall, ideally 3-5 feet above the ground. This is because air moves horizontally as well as vertically, and this placement would ensure that the particles present in either air motion get successfully trapped by the air purifier.


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