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Hay fever


Illustration of a woman who cannot stop sneezing due to hay fever


What is hay fever?


Allergic symptoms caused by plant pollen.


Hay fever is a disease that causes allergic symptoms such as sneezing and runny nose due to pollen, and is called seasonal allergic rhinitis because the symptoms appear during the season when pollen is scattered.


On the other hand, "perennial" allergic rhinitis, which causes symptoms all year round, is mainly caused by house dust and mites.


The main symptoms of hay fever are repeated and sudden sneezing, runny nose, and stuffy nose.

These are called the "three claims" of hay fever.


Other eye symptoms such as itchy eyes, tears, and redness, itchy throat and skin, and systemic symptoms such as headache, feverishness, dullness, sleeplessness, and irritation may occur.


These symptoms cause poor concentration and thinking, feeling unwell, and frustration, and especially interfere with social life such as studying, working, and housework.

Therefore, it is important to take preventive measures and take measures to prevent the deterioration of QOL and to use medicines well.


The main types of pollen that cause hay fever and the time of dispersal vary from region to region.

In Japan, cedar pollen is the most common causative pollen, accounting for 90% of all hay fever patients.

In addition, the amount of Japanese cedar pollen scattered is increasing, which is one of the causes of the increase in pollinosis patients.


How does hay fever occur?


Under normal conditions, pollen is by nature harmless and is not a target for the immune system to work.


However, if pollen is mistakenly recognized as a "foreign substance (antigen)" for some reason, the immune system will work excessively, and allergic symptoms will appear locally, such as in the nose and eyes, mainly due to type 1 allergic reactions.


The trigger for developing hay fever begins when an antigen (pollen) invades the mucous membranes of the nose and eyes, is phagocytosed by macrophages, which are a type of white blood cell, and is recognized as a foreign substance.


Macrophages then pass some of the phagocytosed antigen to Th2 cells.

Th2 cells that receive part of the antigen convey that information to B cells.


B cells that receive information from Th2 cells make antibodies that specifically react with the antigen.

The antibodies produced (such as IgE) are released into the mucosa and attach to the surface of mast cells in the mucosa.


This condition is called "sensitization."

In the sensitized state, no symptoms occur.


In this state, when the same antigen invades the body again and binds to the antibody attached to the surface of mast cells, the structure of the cell membrane changes and chemical mediators such as histamine and leukotriene are released.


Of the chemical mediators released from mast cells, when histamine stimulates the sensory nerves of the nasal mucosa, it causes sneezing and runny nose through the sneezing center, secretory center, and parasympathetic nervous system.


In addition, histamine directly stimulates nasal mucosal blood vessels, causing dilation of blood vessels, congestion of nasal mucosal blood vessels, edema, etc., and causes nasal congestion.


When the action of leukotrienes is added to this, the nasal mucosa further swells and the nasal congestion becomes stronger.

In addition, when histamine acts on the eyes, it causes inflammation, which causes symptoms such as itching, redness, and tearing.


Difference between hay fever and a cold


Photograph of cedar pollen flying from a cedar tree

Perennial allergic rhinitis and colds are misleading disorders that show symptoms similar to hay fever. To make the distinction, you need to see a medical institution.

If symptoms such as rhinitis are strong even with hay fever, it is possible that you have senile rhinitis or pregnant women's rhinitis.


Here, we will pick up colds from among the diseases that need to be differentiated and show the difference from pollinosis.


In the case of hay fever, the symptoms continue for a long time until the causative substance such as pollen disappears, while the cold begins to recover in 3 to 5 days and heals in about 1 to 2 weeks.

In hay fever, fever is low and sneezing is repeated, but in colds, fever is accompanied and coughing is common.


In addition, if the nasal discharge is prolonged due to bacterial infection, the runny nose will change from watery to viscous and yellow.


In addition, hay fever is also characterized by redness and itching of the eyes.

Influenza is suspected, especially if you have a fever of 38 degrees or higher, so you should seek medical attention as soon as possible.


Even if you are diagnosed with hay fever, self-medication is possible in mild to moderate cases.

This degree is determined by the intensity of symptoms of sneezing, runny nose, and stuffy nose.

Moderate is a condition in which you sneeze, blow your nose less than 10 times a day, and sometimes breathe in your mouth due to a stuffy nose.


The following conditions should be taken with a medical institution.

・ Never diagnosed with hay fever in the past

・ It is necessary to distinguish between colds and influenza.

・ Rhinitis other than hay fever

・ Severe cases

・ If you want preventive treatment

・ Infants under 1 year old

・ Pregnant women and lactating women

・ If you have an underlying disease such as glaucoma or difficulty urinating due to enlarged prostate


Pollinosis drug therapy


Antihistamines relieve hay fever symptoms such as itching, runny nose, sneezing, and dilation of nasal mucosal blood vessels by blocking the binding of histamine to H1 receptors.


The chemical mediator release inhibitor suppresses the release of chemical mediator from mast cells, thereby relieving allergic symptoms such as sneezing, runny nose, and stuffy nose.


The vasoconstrictor component acts on the adrenergic α1 receptor and causes vasoconstriction to suppress redness and swelling of the nasal mucosa, improve nasal congestion, and suppress red eye.

Anti-inflammatory and steroidal components have anti-inflammatory effects and relieve inflammatory symptoms of the nasal mucosa and eyes.


Use properly according to the ingredients

If you want to control sneezing and runny nose, select a drug containing antihistamine and anticholinergic components.


The antihistamine component suppresses sneezing and runny nose by preventing histamine released from mast cells from stimulating the sensory nerves of the nasal mucosa.

For the symptoms of stuffy nose, those containing a vasoconstrictor component are effective.

The sympathetic excitatory action constricts the blood vessels of the congested nasal mucosa and relieves nasal congestion.


In addition, the chemical mediator release inhibitor has the effect of suppressing the release of chemical mediators such as histamine and leukotriene released from mast cells, which suppresses the release of allergic symptoms, especially nasal congestion.


For itching of the eyes, we mainly use eye drops containing antihistamine components, chemical mediator release inhibitory substances, and anti-inflammatory components.

 



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