Hay fever is a type of allergic rhinitis caused by pollen or spores. Allergic rhinitis is a condition where an allergen (something that causes an allergic reaction) makes the inside of your nose inflamed (swollen).
Hay fever usually occurs in spring and summer, when there is more pollen in the air. Trees, grass and plants release pollen as part of their reproductive process. Mould and fungi also release tiny reproductive particles, called spores.
People with hay fever can experience their symptoms at different times of the year, depending on which pollens or spores they are allergic to.
Hay fever symptoms vary in severity and your symptoms may be worse some years than others, depending on the weather conditions and the pollen count (see below). Your symptoms may start at different times of the year depending on which types of pollen you are allergic to.
The symptoms of hay fever include:
Less commonly, you may experience:
Hay fever is an allergic reaction
Hay fever symptoms are caused by protein molecules in pollen grains. The immune system ‘over-reacts’ to these allergens, which it manifests in the form of an allergic reaction. Immune molecules known as Immunoglobulin E are produced and these cause the release of the inflammatory chemical called histamine from mast cells (a type of immune cell).
It is histamine that produces the characteristic symptoms of an allergic reaction.
A non-allergic person’s immune system will not produce this reaction on exposure to allergens in pollen.
Hay fever and everyday life
Research shows that students’ academic performance may be affected during exams, given that the exam season usually coincides with the height of the pollen season.
How common is hay fever?
Hay fever is a relatively new disease, first described in 1819. It took nine years to accumulate enough hay fever cases to present a paper on this new condition to a medical journal. Now hay fever is much more common, particularly in the UK, which has more cases than anywhere else in the world (followed closely by Ireland, New Zealand, Australia and Canada). Hay fever:
Hay fever and asthma
If you have asthma, your asthma symptoms may get worse when you have hay fever. Sometimes, asthma symptoms only occur when you have hay fever. These symptoms include:
Hay fever symptoms are likely to be worse if the pollen count is high. The pollen count is the number of grains of pollen in one cubic metre of air.
Air samples are collected in traps set on buildings two or three storeys high. Taking samples from this height gives a better indication of the pollen in the air from both local and distant sources. Traps on the ground would only collect pollen from nearby trees and plants.
The air is sucked into the trap and the grains of pollen are collected on either sticky tape or microscope slides (glass plates). The pollen is then counted. Samples are usually taken every two hours, and the results are averaged for a 24-hour period.
The pollen forecast is usually given as:
Hay fever symptoms usually begin when the pollen count is over 50. The pollen count is usually given as part of the weather forecast during the spring and summer months.
Which pollens are you allergic to?
Spores that cause hay fever can come from:
When is there most pollen?
Different trees and plants produce their pollen at different times of the year.
Depending on which pollen you are allergic to, you may experience your hay fever symptoms at different times. In the UK:
The effect of the weather
The amount of sunshine, rain or wind affects how much pollen plants release and how much the pollen is spread around. On humid and windy days, pollen spreads easily. On rainy days, pollen may be cleared from the air, causing pollen levels to fall
During their pollen season, plants release pollen early in the morning. As the day gets warmer and more flowers open, pollen levels rise. On sunny days, the pollen count is highest in the early evening.
Confusing hay fever with other conditions
A person who appears to be suffering hay fever symptoms may be suffering from:
Alleviating hay fever
It is very difficult to completely avoid pollen or spores. However, reducing your exposure to the substances that trigger your hay fever should ease the severity of your symptoms. Follow the advice below to avoid being exposed to excessive amounts of pollen and spores.
Finally, check the pollen count regularly to know when your efforts need to be more concentrated.
Can an air cleaner help?
While numerous manufacturers of ‘air cleaners’ / ‘air filters’ claim to be able to clear pollen from the air, they can only reduce, not eliminate, the problem, because:
Pets produce dander (microscopic skin flakes that they shed), and the protein in it can cause severe allergic reactions for some people.
Pet dander is a little like dandruff flakes, only smaller; at around 2-3 microns in size it easily becomes airborne and can be inhaled.
Dander can cause allergic reactions for a long period and may persist for many months after the pet has left the house.
The origin of the allergens is in the pet’s urine, sweat and saliva. These excretions adhere to their skin, for example when they clean themselves, and become of the dander they shed.
Cat dander is the most commonly inhaled allergen after house dust mite and pollen. Other types of pet, such as dogs, mice and guinea pigs, may similarly cause allergic reactions.
Because they are so light, pet allergens are widely distributed in the air, remaining airborne for several hours before settling, only to be easily stirred up into the air again.
Clearly, the best way of avoiding pet dander is to not have a pet! However, many of us love our pets too much to do without them! In that case, there are various measures you can take to reduce your exposure, including controlling the pet’s access to certain rooms, and using an effective air purifier to neutralise the dander.
Pet allergies and your health
Pet allergies are known to play a role in:
People with a tendency to allergy (known as atopy), should avoid owning pets if possible. Unfortunately, some people who don’t initially exhibit allergic reactions, can nevertheless develop symptoms after continued exposure.
Why pet dander causes an allergic reaction
Allergens usually enter the respiratory system through the nose. Mast cells in the airways release mediators, which trigger the allergy attack. This attack is an overreaction of the body’s immune system to the invading allergens that have bonded with antibodies. Mast cells are one of the human body’s principal defences against allergens and are found in connective tissue and mucous membranes. One of its biological functions is innate immunity including involvement in host defence mechanisms against parasitic infestations, tissue repair, etc.
Pet dander is very ‘sticky’ and can stay in your hair, clothes and other belongings for long periods of time. This is why you can still suffer symptoms when you are away from the pet causing those symptoms.
The major cat related allergens are found in the cat’s sweat and saliva and the major dog related allergen is found in its saliva.
What animals cause allergy problems?
A wide range of animals can cause allergic reactions including cats, dogs, birds, mice, rats, guinea pigs, rabbits, parrots and hamsters.
Male cats shed more allergen than females, and cats shed more allergen than dogs. Horses produce very powerful allergens and old mattresses stuffed with horsehair can produce symptoms. Snakes, lizards and other reptiles, and even insects, may shed dander-like skin particles into the air.
Perhaps the best pets for a pet allergy sufferer are fish, as they are not associated with allergy!
What about hypoallergenic dogs?
Avoiding pet allergens
Before turning to technological or other solutions, careful allergen avoidance / environmental allergen control is important. For example:
And don't forget - Are you sure pet allergen is really the cause of your allergy? It could be that house dust mite, mould or pollen is the real culprit. An allergy specialist will be able to offer an allergy test to pinpoint the true allergen.
Can an air cleaner help?
While numerous manufacturers of ‘air cleaners’ / ‘air filters’ claim to be able to clear pet dander from the air, they can only reduce, not eliminate, the problem, because:
Pollen allergy, commonly called hay fever, is one of the most common chronic diseases. Worldwide, airborne allergens cause the most problems for people with allergies. The respiratory symptoms of asthma, which affect approximately one in twelve people, are often provoked by airborne allergens.
Although the number of people suffering with an allergy has increased in the last few decades, there is more education and a greater understanding of the immense impact that allergies have on our lives, from allergy symptoms to causes to treatments.
There is no clear explanation for the increase in allergies; however there are two main theories. The first theory is that awareness and diagnosis have improved in recent years and the second is that the increase in general air pollution and indoor air pollution have made allergens more common.
An allergy is characterised by an overreaction of the human immune system to a foreign protein substance (“allergen”) that is eaten, breathed into the lungs, injected or touched and which otherwise does not bother most people.
This immune overreaction can results in symptoms such as coughing, sneezing, itchy eyes, runny nose and scratchy throat. In severe cases it can also result in rashes, hives, lower blood pressure, difficulty breathing, asthma attacks, and even death.
People who have allergies often are sensitive to more than one substance. Types of natural allergens that cause allergic reactions include:
Allergy is not necessarily the same as sensitivity or intolerance to a substance. This is particularly so in the area of food where, for example, lactose intolerance is not classed as a food allergy because the symptoms do not arise from the immune system.
Scientists think that some people inherit a tendency to be allergic from one or both parents. This means they are more likely to have allergies. They probably, however, do not inherit a tendency to be allergic to any specific allergen. Children are more likely to develop allergies if one or both parents have allergies. In addition, exposure to allergens at times when the body’s defences are lowered or weakened, such as after a viral infection or during pregnancy, seems to contribute to developing allergies.
Each IgE antibody is specific to one particular substance. In the case of pollen allergy, each antibody is specific for one type of pollen.
IgE is special because it is the only type of antibody that attaches tightly to the body’s mast cells, which are tissue cells, and to basophils, which are blood cells. When the allergen next encounters its specific IgE, it attaches to the antibody like a key fitting into a lock. This action signals the cell to which the IgE is attached to release powerful chemicals, including histamine, which cause the symptoms of allergy.
The symptoms of airborne allergies are familiar to most people:
In people who are not allergic, the mucus in the nasal passages simply moves foreign particles to the throat, where they are swallowed or coughed out. But something different happens in a person who is sensitive to an airborne allergen.
In sensitive people, as soon as the allergen lands on the lining inside the nose, a chain reaction occurs that leads the mast cells in these tissues to release powerful chemicals, including histamine. These powerful chemicals contract certain cells that line some small blood vessels in the nose, causing fluids to escape and the nasal passages to swell—resulting in nasal congestion. Histamine can also cause sneezing, itching, irritation, and excess mucus production, which can result in allergic rhinitis.
The shortness of breath is due to a narrowing of the airways in the lungs and to excess mucus production and inflammation. Asthma can be disabling and potentially fatal.
Genetics: The risk of having an allergy amongst the general population is around 10-20%. However, If one parent is allergic, a child’s risk rises to 50% and if both parents are allergic, to 75%.
Age, sex, and siblings: On average, children are more likely to suffer from allergy than adults (children can sometimes ‘grow out of’ allergic disease) and the onset can occur at any age. More boys than girls have atopic asthma and hay fever, although this difference reduces in adult life. Children from large families and those with older siblings are less likely to develop allergies, probably because they are more exposed to childhood infection, which makes the developing immune system less likely to over-react to an allergen.
Early-life, or extreme/sudden, allergen exposure: It has been suggested that exposure to allergens like cigarette smoke, traffic pollution, dust, pollen, mould and pet dander in early life may increase a child's risk of developing an allergy. For example breast feeding for six months or more has been shown to decrease the risk of asthma and other allergies in babies. Premature babies are also more at risk of developing allergies than full-term babies.
The most common allergic diseases
Asthma is a disease of the lungs that causes airways to become blocked or narrowed making it difficult for you to breathe. It harder to breathe in than breathe out. Asthma attacks are caused by triggers which are either allergens (like house dust mite, mould, pet dander) or irritants like cigarette smoke, traffic pollution or cold air.
Asthma attacks are usually temporary, but if an asthma episode is severe, a person may need emergency treatment to restore normal breathing. Despite the far reaching effects of asthma, much remains to be understood as to what causes it and how to prevent it.
Asthma is potentially the most serious of the allergic diseases. In the UK, for example, during 2008-9, there were nearly 80,000 hospital admissions for asthma of which nearly half were of children aged 14 and under.
Although asthma can cause severe health problems, in most cases prevention and treatment can control it and allow a person to live a normal and active life.
Hay fever (seasonal rhinitis) is characterised by itchy nose and eyes, sneezing and runny nose. In the UK it is mainly caused by exposure to grass pollen (perennial rye and timothy grass).
Perennial rhinitis persists all year round. Sometimes people with perennial rhinitis do experience worse symptoms in the pollen season. Around 50% of those with perennial rhinitis have an allergy while the rest have some other problem with their nose or sinuses.
The most common airborne allergens
The ‘Allergy Season’
If you are allergic to pollen, you will need to be aware of seasonal variations. Other allergens like house dust mite, traffic and other indoor pollution, tend to be present year-round.
The pollen season varies for different plants and, in the UK, it lasts from early Spring to late Autumn.
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Rhinitis, including hay fever, is the most common of all the allergic diseases. The typical symptoms such as blocked nose, watery eyes, & running nose may persist all year round (perennial rhinitis) or may be seasonal. Even though it’s often undiagnosed and its symptoms often thought of as harmless, the impact perennial rhinitis can have on a person’s overall quality of life can be significant.
What is rhinitis?
Rhinitis is inflammation of the nose. It may, or may not, be caused by an allergy.
Another symptom of perennial allergic rhinitis is post-nasal drip, where mucous runs down the back of the nose and then into the throat and the airways, producing a persistent phlegm cough.
Causes of allergic rhinitis
Allergic rhinitis is caused by exposure to an airborne allergen. Common allergens include:
What happens when the allergen is breathed in
In allergic rhinitis, blood flow is increased, the mucous membranes swell and there is increased mucous production, all occurring in response to histamine production on exposure to the allergen. The result is nasal congestion, nasal blockage, and/or a runny nose.
Allergic rhinitis diagnosis
A simple description of your symptoms and their seasonality may be all that is required to diagnose rhinitis.
If confirmation and/or identification of an allergic cause is needed, then a skin prick test can be used. A tiny drop of allergen extract is placed on the skin at either the arm or the back. If you are allergic to the substance, a small red weal will appear within a short period.
Allergic rhinitis can be reduced by avoiding exposure to allergic triggers, for example:
House dust mite
Medical treatments for allergic rhinitis
If your symptoms are mild, you can use a long-acting non-sedating antihistamine such as Claritin (loratadine), NeoClaritin (desloratadine), Zyrtec (cetirizine), Xyzal (levocetirizine) or Allegra (fexofenadine). These are available without a prescription, but you should always consult your pharmacist before use.
The older antihistamines like chlorpheniramine (Piriton) and hydroxyzine (Atarax) have a significant sedating effect and should not be used if you are driving, operating machinery, or studying. These older drugs also interact with alcohol so having even a small amount to drink may significantly affect performance.
If rhinitis mainly affects your eyes, antihistamine eye drops, such as Otrivine (antazoline) may help.
In addition to an antihistamine, a nasal decongestant (drops or a spray) may also be helpful in clearing a blocked nose. Some of these decongestants are corticosteroids, which act by reducing inflammation including Beconase (beclomethasone) and Flixonase (fluticasone). Non-corticosteroid nasal decongestants include Otrivine/Sudafed (xylometazoline). All of these can be bought without a prescription. However, only use a decongestant for as short a time as possible, as the nose tends to stop responding to these medications over time.
In general, antihistamines and topical nasal steroids are most effective against seasonal allergic rhinitis/hay fever but may still help with perennial allergic rhinitis.
Can an air cleaner help?
While numerous manufacturers of ‘air cleaners’ / ‘air filters’ claim to be able to clear those allergens leading to rhinitis from the air, they can only reduce, not eliminate, the problem, because:
Asthma has become one of the most common chronic disorders in the developed world. Asthma is difficult to describe, but the International Consensus Report on the Diagnosis and Management of Asthma defines it the following way: “Asthma is a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role".
Throughout the developed world, typically 5% of adults and 10% of children have clinically significant asthma. Its prevalence has increased significantly over the last 25 years and is now thought to affect around 300 million people worldwide.
Asthma can be a serious condition, which occasionally proves fatal, accounting for 1,131 deaths in the UK in 2009. However, most deaths and hospital admissions for asthma are preventable. Asthma is a condition that can be managed successfully and part of that management should include a strategy for allergen avoidance.
For example, in the UK, around 5.4 million people suffer from asthma, which includes 1.1 million children. The condition costs health services around £1 billion a year and accounts for an annual 1.1 million lost working days and around 80,000 hospital admissions.
Asthma comes in several forms
There are two primary types of asthma – childhood onset and adult onset. Most asthma does begin in childhood and is often associated with other related conditions like eczema and rhinitis.
Childhood onset asthma often has clearly identifiable triggers which will bring on an attack.
Adult onset asthma may be a continuation of childhood onset asthma, or it may be a new onset of the condition. Asthma can occur at any age, and should be considered in anyone who has a chronic cough. In adult onset asthma, there is often no obvious trigger, except for a chest infection.
There are also several sub-categories of asthma, including:
It can run in families
Asthma tends to run in families. However, asthma is not a single-gene disorder, with a clear line of inheritance. There are several ‘susceptibility’ genes involved in asthma, each contributing to the risk of developing the disease.
Diagnosis depends upon the doctor taking a careful medical history from the patient and noting whether the hallmark symptoms of wheeze, chest tightness, breathlessness, and cough are present. There are no laboratory or other tests which can definitely diagnose asthma and distinguish it from other lung conditions. However, if your doctor suspects asthma you may be subject to breathing tests to help confirm the diagnosis. Such tests include:
Spirometry: Spirometry is breathing into a machine which measures how much air you can exhale, which shows whether the airways are obstructed or not.
Peak expiratory flow rate test: A small hand-held device, called a peak flow meter, is used to measure how fast you can blow air out of your lungs in one breath. The peak flow meter can be a useful tool to use yourself at home to monitor your asthma.
Skin prick, or blood tests, are often carried out to find out which allergens might be triggering your asthma.
Thorough diagnosis by a doctor is a must, as asthma can easily be mistaken for other conditions, including:
Asthma tends to be a chronic disease (that is once you have asthma it will remain with you for the rest of your life). However, around a half of children do ‘grow out of’ asthma by the time they become teenagers, sometimes to re-emerge in adulthood. Like other chronic diseases, such as diabetes, asthma is not curable in the same way that, say, an infection can be cured. However, asthma can be controlled successfully so you can still live a full life.
Dr Wyatt blogs on his lifetime's experience of Indoor Air Quality Issues.