What is allergic rhinitis?
Allergic rhinitis is a group of diseases characterized by sneezing, nasal itching, airflow obstruction, and clear, bright nasal discharge. Allergens include seasonal pollen, mold and dust.
Early diagnosis of allergic rhinitis is difficult because of the frequency of respiratory viral infections in adolescents and the similarity of symptoms to allergic rhinitis. In severe cases, allergic rhinitis can seriously affect school, work, sleep and limit outdoor activities.
How is it diagnosed?
Clinical diagnosis depends on the symptoms and the response to treatment with antihistamines and nasal glucocorticoids. The diagnosis is usually based on the discovery of clear evidence of sensitization and the presence of symptoms associated with exposure to the allergen. Evidence of sensitization is defined as the presence of allergen-specific IgE antibodies in the serum or a positive skin test.
IgE antibodies or a positive skin test. The diagnostic efficacy of these 2 methods is similar, but they do not cover all cases.
The advantages of the serum test for allergen-specific IgE antibodies are that the patient does not have to stop taking antihistamines several days in advance and that the procedure does not require sophisticated techniques. The advantage of the skin test is that the results are available immediately.
Drug therapy
These include H1-antihistamines, intranasal administration of glucocorticoids and leukotriene receptor antagonists.
Pharmacological and allergen immunotherapy for allergic rhinitis
Treatment is usually started with oral antihistamines. New generation antihistamines are recommended because of their milder sedative effect compared to older generation antihistamines. Because of their rapid onset of action, antihistamines can be used as a basic treatment when necessary. Nasal antihistamines are similar in efficacy to oral antihistamines, but the oral experience is poor (bitter taste).
Antihistamines are moderately effective in relieving nasal congestion and can improve nasal breathing when combined with oral decongestants. Nasal decongestants are more effective than oral decongestants, but cases of rebound after using nasal decongestants have been reported; in addition, nasal decongestants are only recommended for short-term use.
For seasonal allergic rhinitis, intranasal administration of glucocorticoid therapy is the most effective treatment, but the overall efficacy is moderate. The advantages of intranasal glucocorticoid therapy over antihistamines are not clear in patients with perennial allergic rhinitis.
Leukotriene receptor antagonists are similar to or less effective than antihistamines in relieving the symptoms of allergic rhinitis, and there have been isolated cases where the combination of leukotriene receptor antagonists with antihistamines has been shown to be more beneficial. This combination may be used in patients who are not well controlled with antihistamines and who do not want to use glucocorticoids.
Allergen immunotherapy
It is estimated that 1/3 of children and nearly 2/3 of adults with allergic rhinitis experience only mild relief with pharmacologic treatment. The next step in the treatment of these patients is allergen immunotherapy.
One type of immunotherapy is subcutaneous allergen immunotherapy: the patient receives increasing concentrations of allergen until a maintenance dose is reached. The other is sublingual allergen immunotherapy: the patient receives a fixed dose of allergen 12-16 weeks prior to the onset of the allergy season. Both of these methods, of course, require maintenance doses for several years.
Allergen immunotherapy not only controls allergic rhinitis, but also helps control allergic asthma and conjunctivitis. Unlike drug therapy, the efficacy of allergen immunotherapy persists after termination of treatment. A 3-year subcutaneous allergen immunotherapy (grass extraction) has been reported to continue for at least 3 years after termination of treatment.
A disadvantage of subcutaneous immunotherapy is that it requires 1-2 weekly injections as the allergen dose is built up gradually; for maintenance dose therapy, monthly injections are given. If there is improvement in symptoms in the 1st year, injections often need to be continued for at least 3 years. Subcutaneous allergen therapy carries the risk of causing systemic reactions and, in very rare cases, life-threatening systemic anaphylaxis (probability 1 in 1 million).
Indirect comparisons suggest that subcutaneous allergen immunotherapy is more effective than sublingual immunotherapy in reducing symptoms, but sublingual immunotherapy is safer and rarely causes systemic adverse reactions. Unlike subcutaneous immunotherapy, sublingual immunotherapy can all be administered at home after the initial dose, but needs to be administered daily.
Uncertainty
The appropriate use of immunotherapy, the duration of stimulation, and the length of maintenance are still uncertain. It is also unclear whether multiple allergen therapy is more effective than single allergen therapy. It is currently recommended that allergen immunotherapy be recommended only for those patients who do not have significant symptom control after pharmacologic therapy and for those who prefer immunotherapy.
Treatment may be empirical and if symptoms do not decrease significantly after treatment, sensitization testing for the relevant allergen should be performed to diagnose allergic rhinitis. The choice of treatment regimen should take into account the severity of symptoms and the corresponding drug regimen.
Review of key points
1. Allergic rhinitis is highly prevalent and can affect the quality of life of children and adults.
2. People with allergic rhinitis often have a combination of asthma and other allergic diseases, and many people with asthma have rhinitis.
3. Intranasal administration of glucocorticoids is often the preferred treatment option. Oral, intranasal administration of antihistamines and leukotriene receptor antagonists are alternative options. However, many patients do not experience any reduction in their disease after receiving medication.
4.For those patients with refractory symptoms or severe adverse reactions caused by drug therapy, allergen immunotherapy should be performed.
5.There are 2 types of allergen immunotherapy.
(1) Subcutaneous injection;
(2) sublingual tablet.
The 2 methods continue to be effective even after the treatment is stopped.
Therefore, the clinical diagnosis of allergic rhinitis is mostly dependent on the symptomatic manifestations and the response to antihistamine and nasal glucocorticoid therapy. The diagnosis is usually based on the discovery of clear evidence of sensitizing effects and the presence of corresponding symptoms of exposure to the allergen.