Etiology
Allergic rhinitis is a multifactorial disease triggered by the interaction of genes and the environment. Risk factors for allergic rhinitis may exist in all age groups.
1. Genetic factors
Patients with allergic rhinitis have atopic constitution and usually show family aggregation.
2.Allergen exposure
Allergens are antigens that induce specific IgE antibodies and react with them. They are mostly derived from animals, plants, insects, fungi or occupational substances. Their composition is proteins or glycoproteins and very rarely polysaccharides. Allergens are mainly divided into inhalant allergens and food allergens. Inhalant allergens are the main cause of allergic rhinitis.
(1) Mites in the subtropical and tropical regions are the most important mites such as house dust mite and dust mite. House dust mites feed on human dander and live mainly in mattresses, bed bottoms, pillows, carpets, furniture and plush toys. They reproduce fastest in hot (above 20°C) and humid (relative humidity >80%) environments. House dust mite allergens are contained in their excrement particles, which are exposed to the air and can be quickly re-deposited when the contaminated fabric is touched. The concentration of mite allergens in the air is associated with the onset of allergic rhinitis.
(2) Pollen wind-borne pollen can affect people hundreds of kilometers away from the pollen source because of its huge dispersion and ability to travel long distances. Insect-borne pollen can only be sensitized by direct contact, such as agronomists and florists. The allergenic capacity of pollen varies with season, geographic location, temperature and plant species. Most pollen sensitizers will suffer from conjunctivitis.
(3) Animal dander animal dander and secretions carry allergens. Cat and dog allergens are widely present in house dust and furniture decorations.
(4) fungal allergens mold to indoor and outdoor environment to release allergenic spores, hot and humid environment grows rapidly.
(5) Cockroach allergens are found in their feces and carapace, and the particles are large and do not spread in the air.
(6) Food allergens are rare when allergic rhinitis is not accompanied by other systemic symptoms.
Clinical manifestations
The typical symptoms of allergic rhinitis are mainly paroxysmal sneezing, clear watery nose, nasal congestion and nasal itching. Some of them are accompanied by hyposmia.
1.Sneezing
Paroxysmal attacks several times a day, more than 3 each time, mostly in the morning or at night or immediately after contact with allergens.
2.Clear mucus
A large amount of clear nasal discharge, sometimes unconsciously dripping from the nostrils.
3.Nasal congestion
Intermittent or persistent, unilateral or bilateral, with varying degrees of severity.
4.Itchy nose
Most of the patients have itching in the nose, and hay fever patients may have itchy eyes, ears and throat.
Examination
1. Physical signs
Pale nasal mucosa, edema of both inferior turbinates, clear or mucus in the common nasal passage and nasal floor.
2.Dermal prick test
Using standardized allergen reagent, skin prick on the palm side of forearm and observe the result after 20 minutes. Positive and negative controls should be performed for each test, with histamine used for the positive control and allergen lysis medium used for the negative control. The results should be determined according to the corresponding standardized allergen reagent instructions. The skin prick test should be performed at least 7 days after discontinuation of antihistamines.
3.Serum specific IgE test
The patient’s venous blood is drawn and the immunological test is done independent of the drug and skin condition. The diagnosis of allergens in allergic rhinitis requires a combination of clinical history, skin prick test, and serum specific IgE test results.
4.Nasal excitation test
It is the gold standard for the diagnosis of allergic rhinitis, but it has risks and is not used as a routine clinical method.
Diagnosis
Clinical symptoms sneezing, clear watery mucus, nasal congestion, nasal itching and other symptoms appear more than 2 (including 2), and the symptoms last or accumulate for more than 1 hour per day. It may be accompanied by eye symptoms such as itchy eyes and conjunctival congestion. Signs commonly include pale, edematous nasal mucosa and aqueous nasal discharge. Allergen skin prick test is positive and/or serum specific IgE is positive, and nasal provocation test is feasible if necessary.
Differential diagnosis
Allergic rhinitis needs to be differentiated from acute rhinitis catarrhal phase, cerebrospinal fluid rhinorrhea, and vasomotor rhinitis.
Complications
Complications of allergic rhinitis can be classified as the same pathogenic pathway (e.g., allergic reactions) or in combination with other diseases (mucosal swelling, co-infection due to mucus retention). These include asthma, conjunctivitis, chronic rhinosinusitis, adenoid hypertrophy, and secretory otitis media. The presence of allergic rhinitis aggravates asthma, and most asthmatics suffer from allergic rhinitis. Outdoor allergens are more likely to cause allergic conjunctivitis than indoor allergens[1] .
Treatment
1. Avoid exposure to allergens
(1) Reduce the number of dust mites indoors; maintain the relative humidity of the living space to below 60%, but too low (e.g., below 30%-40%) will cause discomfort; clean carpets; wash bedding and curtains; mite allergens are soluble in water, and washing textiles can remove most of them; use air purifiers and vacuum cleaners with filters, etc.
(2) Avoid allergens in the corresponding pollen allergy season.
(3) Avoid allergens for patients allergic to animal fur.
2. Drug treatment
Intranasal and oral medications are commonly used, and their efficacy may vary from patient to patient. There is no long-term sustained efficacy after discontinuation of medication, so maintenance treatment is required for persistent allergic rhinitis. Prolonged treatment does not result in rapid drug resistance. Various drugs should be used with caution in patients during pregnancy.
(1) Antihistamines oral or nasal 2nd generation or new H1 antihistamines are effective in relieving symptoms such as nasal itching, sneezing and runny nose. It is suitable for mild intermittent and mild persistent allergic rhinitis, and combined with nasal glucocorticoids for moderate-to-severe allergic rhinitis.
(2) Glucocorticoids Nasal glucocorticoids can effectively relieve symptoms such as nasal congestion, runny nose and sneezing. Severe patients who do not respond to other medications or cannot tolerate nasal medications can be treated with oral glucocorticosteroids for a short period of time.
(3) Anti-leukotrienes are effective in allergic rhinitis and asthma.
(4) Chromones are effective in relieving nasal symptoms, and eye drops are effective in relieving ocular symptoms.
(5) Intranasal decongestants are effective in relieving nasal congestion caused by nasal congestion, and the course of treatment should be controlled within 7 days.
(6) Intranasal anticholinergic drugs can effectively inhibit runny nose.
(7) Some herbal medicines are effective in relieving symptoms. The treatment principles for children and the elderly are the same as those for adults, but special attention should be paid to avoid the adverse reactions of drugs.
3.Immunotherapy
Immunotherapy induces clinical and immune tolerance with long-term effects and can prevent the development of allergic diseases. Allergen-specific immunotherapy is commonly administered by subcutaneous injection and sublingual administration. The course of treatment is divided into a dose accrual phase and a dose maintenance phase, with a total duration of not less than 2 years. Standardized allergen vaccines should be used.
(1) Indications are mainly for patients with allergic rhinitis for whom conventional drug therapy is ineffective.
(2) Contraindications (contraindications exist and are not appropriate for all patients) ① during asthma exacerbations; ② patients are using beta-blockers; ③ in combination with other immune diseases; ④ women during pregnancy; ⑤ patients are unable to understand the risks and limitations of treatment. Immunotherapy may have local and systemic adverse effects.
4.Surgical treatment: some patients can be operated
The indications are no improvement of nasal congestion symptoms by drug or immunotherapy, with obvious signs, affecting the quality of life; obvious anatomical variation of the nasal cavity with dysfunction; combined with chronic rhinosinusitis, nasal polyps, and ineffective drug treatment. Surgical treatment is not used as a routine treatment for allergic rhinitis.