hay fever



Overview

Allergenic pollen-induced type I allergic disease after contact with pollen, nasal congestion, runny nose, itching, sneezing, red eyes, photophobia, asthma and other manifestations of the treatment is mainly to avoid allergens, the cause of the treatment can not be a complete cure, the need to avoid contact with pollen in daily life.

Definition

Pollen allergy, also known as hay fever, is an allergic disease caused by inhalation of or contact with pollen in patients with atopic constitution. Allergens (allergens) are special proteins within pollen.

Clinically, pollen-induced allergic rhinitis, allergic conjunctivitis, asthma, urticaria, and atopic dermatitis are collectively referred to as hay fever [1]. Symptoms are often exacerbated during pollen-borne seasons (spring, summer and early fall).

Classification

Based on the type of pollen that causes an allergic reaction, hay fever can be categorized as follows:

Tree hay fever

Allergic reactions caused by pollen from trees such as birch, oak, poplar and elm.

Herbaceous hay fever

Allergic reactions caused by herbaceous pollen, such as corn, wheat, sorghum, dogwood, etc.

Weed hay fever

Allergic reactions caused by weed pollen, e.g., thistle, mugwort, ragweed, etc. [2-3].

Morbidity

The prevalence of hay fever worldwide is about 30%, the allergy rate of ragweed pollen in the United States is 26%, and the prevalence of hay fever in Europe has risen to 20% in the last 20 years.

The prevalence of hay fever in China is 0.5% to 1%, and it can reach 5% in high incidence areas. Some scholars reported that the prevalence of allergic rhinitis in Inner Mongolia was 32.4%, of which the prevalence of hay fever was as high as 18.5% [4-6].

The occurrence of hay fever is closely related to the season of pollen transmission. Overseas hay fever mainly occurs in spring, summer and fall in the three seasons of tree pollen, pasture pollen and weed pollen.

The seasonal distribution characteristics of airborne pollen in most cities in China show two peaks in spring and fall. The content of airborne pollen in summer and winter is relatively small.

Spring is dominated by the flowering of trees, including pine, cypress, poplar and mulberry. Herbs with strong allergenicity bloom more in fall, including Artemisia, Grasses, Ragwort, Quinoa and Araceae. Because of the gradual drying of the climate in autumn, which is conducive to pollen transmission, and the strong allergenicity of plant pollen, the incidence of hay fever in autumn is the highest in China, and it is especially prominent in the northern region [7].

Etiology

Hay fever is an allergic disease related to genetics, environment and lifestyle. In susceptible people, the immune system produces excessive antibodies after inhaling pollen, triggering an inflammatory response.

Causes

Hay fever is a type I allergic disease induced by sensitizing pollen. Airborne allergenic pollens are pollens that are windborne and contain specific proteins that cause hypersensitivity in sensitive individuals. Hay fever is usually associated with the following factors.

Genetic factors

Genetic factors play an important role in the development of hay fever. Studies have shown that children who have at least one parent with an allergic condition (e.g. hay fever, asthma, atopic dermatitis, etc.) are more likely to develop hay fever. In addition, some genetic variants may increase an individual’s risk of pollen allergy.

Environmental factors

The concentration of pollen in the environment is a direct cause of hay fever. Factors such as climate change, vegetation distribution, wind direction and air pollution may affect pollen dispersal and concentration. In addition, high air pollution levels may exacerbate pollen-induced allergy symptoms.

Lifestyle

Lifestyle may also influence the occurrence of hay fever. For example, people living in urban environments may be more susceptible to hay fever than those living in rural environments, as urban air pollution may increase sensitivity to pollen.

Early exposure to allergens, overuse of antibiotics, and lack of exposure to microorganisms found in traditional rural environments may also be associated with the development of hay fever [3,8].

Pathogenesis

When a susceptible individual inhales pollen, specific proteins in the pollen react with certain components of the immune system. This causes immune cells to produce excessive amounts of IgE antibodies.

When IgE antibodies bind to pollen, they activate mast cells and eosinophils, releasing inflammatory mediators such as histamine and leukotrienes. These inflammatory mediators further cause inflammatory reactions in local tissues such as runny nose, sneezing, nasal congestion and ocular itching [9].

Risk factors

People with one or more of the following factors are at high risk for hay fever:

Family history: people with a family history of allergic diseases are more likely to develop hay fever.

Age: children and adolescents are more likely to develop hay fever.

Other allergic diseases: People with asthma, atopic dermatitis or other allergies are more likely to develop hay fever.

Environmental exposure: People who live in areas with high pollen concentrations are more likely to develop hay fever.

Symptoms

Hay fever is mainly characterized by itchy nose, sneezing, runny nose and nasal congestion, which may be accompanied by cough, asthma and rash. Pollen in the eyes may cause conjunctivitis and keratitis.

Main symptoms

Whole pollen can cause dermatitis and conjunctivitis/rhinitis by direct contact, and asthma by inhalation of pollen fragments into the lower airways [10-12]. The main symptoms of hay fever include:

Nasal symptoms

Itchy nose: may involve the eyes, throat, and ears.

Sneezing: continuous sneezing, usually sudden. Usually 5 to 20 occur in a single episode.

Runny nose: common in the early stages of hay fever. The nose constantly produces a large amount of clear snot to keep it clean, causing the person to keep blowing their nose.

Nasal congestion: 50% of hay fever sufferers have nasal congestion. The mucus in the nose is congested and swollen, resulting in blocked nasal passages. As you can only breathe through your mouth, you may feel dry mouth in the morning and in severe cases, you may lose your sense of smell and taste.

Symptoms in the trachea and lungs

Cough: In the early stages it can often present as cough variant asthma, with a cough lasting >4 weeks, often attacked or exacerbated by exercise and at night.

Asthma: Inhalation of small particles of pollen or debris pollen can trigger asthma. Some patients develop asthma after coughing for some time.

Skin symptoms

The rash of hay fever dermatitis is often symmetrical and itchy, accompanied by an increase in skin temperature, which manifests as urticaria, eczema and angioedema.

Eye symptoms

When pollen enters the eyes, it can cause conjunctivitis (manifested as redness, itching and swelling of the eyes, etc.) and keratitis (manifested as pain in the eyes, tearing and photophobia, etc.). Some pollen particles accumulate in the corners of the eyes so that people can’t help rubbing them with their hands, which further irritates the eyes and makes the itching worse.

Complications

Acute sinusitis

Due to swelling and inflammation of the nasal mucosa, sinus passages may be obstructed, leading to bacterial infection and sinusitis. Symptoms of acute sinusitis include facial pain, headache, nasal congestion, runny nose (which may be thick and yellow or green), fever and sore throat.

Worsening of asthma

Hay fever may lead to worsening of asthma symptoms, especially during seasonal pollen peaks. Symptoms of worsening asthma include shortness of breath, wheezing, coughing and chest tightness.

Otitis media

Inflammation of the nasal mucosa may lead to obstruction of the Eustachian tube (the tube that connects the nasopharynx to the middle ear), which in turn leads to otitis media. Symptoms of otitis media include earache, hearing loss, pressure sensation in the ear, headache and fever.

Sleep disorders

Due to nasal congestion and breathing problems, hay fever sufferers may experience reduced sleep quality, snoring and drowsiness at night.

Nasal polyps

Prolonged inflammation of the nasal mucosa may lead to the formation of nasal polyps. Nasal polyps are non-cancerous, soft tissue growths that may lead to symptoms such as nasal congestion, dyspnea, and decreased sense of smell [13].

Seek medical attention.

When hay fever symptoms appear, consult an allergist; for severe symptoms, seek emergency medical care; for nasal, eye, and skin symptoms, consult an otorhinolaryngologist, ophthalmologist, or dermatologist.

Where to go for medical treatment

Department of Allergy

If you have itchy eyes and nose, runny nose, sneezing and coughing after exposure to pollen, and the symptoms are not relieved after leaving the environment, you should consult the Department of Metabolic Reactions promptly.

Emergency Department

After exposure to pollen, if there are emergencies such as persistent cough, erythema all over the body, respiratory difficulty or even loss of consciousness, you should go to the Emergency Department or call 120 emergency immediately.

Other Departments

If the allergen is unknown and you only have nasal, eye or skin symptoms, you can also go to the corresponding ENT, ophthalmology or dermatology department.

Preparation

Preparing for your visit: registering, preparing your documents, FAQs

Tips for visiting the doctor

Record the name of the plant you were exposed to, and the time, place, and duration of the allergic symptoms.

Prepare photos of allergic symptoms, such as red, swollen skin and nasal congestion.

Preparing for medical treatment

Symptom list

Pay particular attention to the time of onset of symptoms, special manifestations, etc.

What are the symptoms of discomfort?

When did they occur? Where were you at the time?

Are the symptoms constant or intermittent? What is the frequency of attacks?

Are the symptoms seasonal? During which seasons are the symptoms worse?

Medical History Checklist

Any allergic diseases such as asthma, allergic rhinitis, food allergies, etc.?

Live in urban or rural areas?

What occupation do you work in? Need to be exposed to pollen?

Do parents or siblings suffer from allergic diseases (e.g. allergic rhinitis, food allergies, etc.)?

What treatments have you received after the onset of the disease? What is the effect of treatment?

Checklist

Test results in the last six months, which can be brought to the doctor’s office

Serum IgE test, skin prick test, provocation test, etc.

Medication list

Medication used in the last 3 months, if available, bring along the box or package for medical consultation

Antihistamines (oral): loratadine, cetirizine, etc.

Glucocorticoids (oral or injectable): fluticasone, budesonide, prednisone, etc.

Diagnosis

Diagnosis of hay fever is mainly based on medical history, clinical manifestations, allergen skin test and serum specific IgE test.

Diagnosis is based on

Medical history

Suspected correlation with pollen exposure.

Seasonality of onset.

Family history of allergic diseases.

History of other allergic diseases such as atopic dermatitis and asthma.

Clinical manifestations

Nasal symptoms such as runny nose, sneezing, nasal congestion and nasal itching after pollen exposure.

There are bronchial or pulmonary manifestations such as cough and asthma.

There are skin and eye manifestations such as skin erythema, eye redness, eye itching and tearing.

Pollen allergen testing

Allergen testing is divided into in vivo testing (also known as skin testing) and in vitro testing. In vivo tests include intradermal test, prick test, excitation test, patch test and so on. In vitro tests include serum-specific Ig E test.

Prick test

A drop of the tested allergen extract is placed on the surface of the skin, and a puncture needle is used to gently pierce the skin through the drop to the extent that it does not cause bleeding. It is a precise method of inducing an IgE antibody response. The skin prick test is more specific and safer than the intradermal test in confirming the diagnosis of allergic diseases.

Serum Specific IgE Test

Determines the specificity of the patient’s blood for pollen allergens according to immunological principles. It is used in the following cases:

Patients who can discontinue medications that interfere with the skin test.

Patients who may have a history of extreme sensitivity to allergens.

Patients with positive skin scratches and extensive skin disease that precludes in vivo testing.

Children under 5 years of age.

Patients with severe symptoms who are unable to discontinue symptomatic treatment that would interfere with skin test results.

Differential Diagnosis

The following diseases are associated with runny nose, sneezing and nasal congestion, and hay fever needs to be differentiated from these diseases.

Colds

Colds may be accompanied by fever, muscle aches and malaise, which are not usually present in hay fever. Symptoms of colds are usually short-lived (around 1 week), whereas symptoms of hay fever may last longer during pollen season.

Chronic rhinitis

Symptoms of chronic rhinitis last longer (more than 12 weeks), while symptoms of hay fever are usually worse during pollen season. In addition, chronic rhinitis may be accompanied by symptoms such as foreign body sensation in the nose, decreased sense of smell and headache.

Sinusitis

Sinusitis may be accompanied by symptoms such as facial pain, pressure, headaches and yellow-green nasal discharge, which are not usually present in hay fever.

Treatment

Aims of treatment: Relief of symptoms, reduction of allergic reactions and improvement of the patient’s quality of life.

Principles of treatment: Allergens should be avoided in the first place, and treatment is divided into flare-up treatment and remission treatment.

Removal of triggers

The first step in treatment is to avoid allergens.

During the pollination season of airborne pollen, midday and afternoon are at the peak of the day, so outdoor activities should be avoided and windows and doors should be kept closed during these times.

In some countries and regions, pollen maps have been specially drawn to provide guidance for local residents as well as people on business trips and travelers to avoid allergenic pollen [12].

Flare-up period

Patients with hay fever should be given adequate treatment with anti-inflammatory drugs during the pollination season corresponding to their allergenic pollen. Some studies have shown that prophylactic use of anti-allergic medications should be started as early as 2 weeks before the pollen season [14-15].

Medication

Glucocorticoids.

Have strong anti-inflammatory effects and can control the acute inflammatory response in a short period of time.

Topical application: commonly used for nasal or inhalation. The side effects of hormones are significantly reduced because of topical application, which is effective and has little systemic absorption. Commonly used drugs include fluticasone and budesonide.

Injection use: For patients with moderate to severe hay fever, injection of long-acting glucocorticoid is needed when the application of antihistamines and topical glucocorticoid cannot relieve the symptoms well.

Antihistamines

They can effectively control the acute nasal and ocular symptoms of hay fever, but cannot inhibit the progression of the disease. Commonly used drugs include loratadine and cetirizine. Choose nasal or oral administration according to the situation.

For those with ocular symptoms, antihistamine eye drops, such as emetine fumarate eye drops, can be used.

Leukotriene receptor antagonists

They can be used to relieve nasal symptoms such as nasal congestion and sneezing, as well as for the prevention and long-term treatment of asthma. Commonly used drugs include montelukast sodium.

Other treatments

Pollen blockers

Some studies have indicated that applying pollen blockers in the nasal cavity can be an intervention [16].

Nasal rinsing

From the experience of clinical application at home and abroad, although nasal rinsing does not have a direct anti-inflammatory effect, nasal rinsing in combination with antihistamines and nasal glucocorticosteroids can enhance the efficacy of the drugs and reduce the amount of drugs used, which can be used as a safe and effective complementary treatment for allergic rhinitis [17].

Remission

Atopic immunotherapy

The therapy is allopathic. Currently, allergen-specific immunotherapy (AIT) is commonly used in clinical practice and is the first-line treatment for pediatric patients. It includes subcutaneous injection and sublingual administration.

The mechanism is to identify the causative allergen, and then use the allergen infusion to gradually increase the dose through different routes to produce closed antibodies, forming an immune effect. After the treatment, the body is exposed to the natural environment with only minor symptoms or even no symptoms.

It is suitable for the following situations: allergy symptoms cannot be adequately controlled by allergen avoidance and anti-inflammatory drug treatment; high-dose anti-inflammatory drugs and/or a combination of multiple anti-inflammatory drugs are needed to control allergy symptoms; adverse reactions occur during the treatment with anti-inflammatory drugs; patients want to avoid long-term treatment with anti-inflammatory drugs [10].

Prognosis

The prognosis of hay fever varies from person to person; symptoms can be controlled but require long-term management, which may affect quality of life and cause sleep and psychological problems.

Cure

The prognosis of hay fever varies from individual to individual. In general, timely treatment measures can be effective in controlling symptoms and improving quality of life. However, hay fever may recur and patients need long-term symptom management. It can be life-threatening if severe asthma is induced and treatment is not timely.

Harmful

Impaired quality of life

Hay fever may have a significant impact on a patient’s daily life, resulting in limited school, work and social activities. Prolonged nasal congestion, runny nose and sneezing may lead to problems such as reduced sleep quality, poor concentration and fatigue.

Psychological effects

Chronic symptoms may lead to psychological problems such as anxiety, depression and impaired self-esteem. These psychological problems may further affect the patient’s quality of life and relationships.

Daily

Daily management of hay fever includes avoiding allergens, paying attention to pollen concentration, maintaining indoor cleanliness and good living habits, and avoiding irritating foods and alcohol. Patients with skin symptoms should pay attention to skin care, and those with eye symptoms should avoid excessive eye use.

Daily Management

Life management

Avoid contact with allergens as far as possible, especially during pollen season.

Pay attention to the forecast of pollen concentration issued by the meteorological department and choose appropriate protective measures according to the forecast, such as wearing masks, avoiding outdoor activities and closing windows.

Keep indoor air clean and use air purifiers.

Clean furniture, carpets and curtains regularly to minimize the accumulation of allergens.

Maintain good living habits, including regular work and rest, proper exercise, etc. to strengthen body immunity.

Dietary management

Avoid drinking alcohol.

Avoid spicy and irritating foods (e.g. chili peppers, onions, ginger, garlic), as well as foods that may aggravate allergic symptoms, such as shrimp, mutton and seafood.

Others

If there is rash or itchy skin, avoid scratching, rubbing or cleaning the skin with soap and water, etc. to minimize trauma and bleeding.

If there are eye symptoms, avoid prolonged close eye use.

Follow-up and review

Review regularly, determine the review cycle according to the symptoms and doctor’s recommendation.

Review items include allergen skin prick test, serum specific IgE test, etc. to assess the change of allergy symptoms and treatment effect.

If symptoms worsen during treatment or new symptoms appear, consult your doctor promptly.

Prevention

Prevention of hay fever focuses on reducing exposure to pollen and reducing the risk of allergic reactions.

Pay attention to pollen seasons and pollen counts

Learn about the local pollen season and major allergens, and pay attention to the pollen counts provided by the Met Office or relevant websites. Minimize outdoor activities on days with high pollen counts.

Close windows and doors

During pollen season, try to close windows and doors in your home and car to minimize the chance of pollen entering the house. Consider using an air purifier to reduce indoor pollen levels.

Wear a mask when going out

Wear a mask when going out during pollen season to minimize the chance of inhaling pollen. Wearing a mask can be effective in reducing pollen inhalation especially during outdoor activities and sports.

Regular Cleaning

Keep your house clean and wash carpets, curtains and furniture surfaces regularly to minimize pollen deposition. Use a vacuum cleaner with a high efficiency filter for cleaning.

Bathing and changing clothes

During pollen season, take a shower and change clothes and shoes promptly after coming home from outside to minimize the chance of bringing pollen indoors.

Avoid drying clothes

During pollen season, try to avoid drying clothes outdoors to prevent pollen from attaching to them.

Pet care

If you have pets, bathe and groom them regularly to minimize the chances of bringing pollen indoors.

Maintaining indoor humidity

Maintain proper indoor humidity (about 40% to 60%) to minimize the suspension time of pollen in the air.