allergic cough

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OVERVIEW

排除哮喘或嗜酸性粒细胞性支气管炎，与特应性致病因素有关的慢性咳嗽
症状主要为阵发性、刺激性干咳，常伴有咽喉发痒
病因尚不明确，可能与变应性疾病或易过敏的特应性体质有关
糖皮质激素及抗组胺药物等治疗有效

Definition.

  • Allergic cough is a type of chronic cough defined as a cough that has been present for ≥8 weeks in adults or ≥4 weeks in children.
  • Allergic cough is a chronic cough caused by atopic pathogenic factors, with normal sputum eosinophils, no airway hyperresponsiveness, and effective treatment with glucocorticoids and antihistamines, but not diagnostic of asthma or eosinophilic bronchitis.
  • There is a lack of extensive systematic studies.

    • Morbidity

    There are no national epidemiologic data on allergic cough.

  • In 2006, a study in Guangzhou showed that 12.3% of chronic cough patients seen in outpatient clinics had allergic cough.
  • In 2013, a prospective, multicenter study in China showed that 13.2% of chronic cough patients seen in general hospitals had allergic cough.
  • In 2016, a study in Lanzhou showed that 11.56% of chronic cough patients seen in outpatient clinics had allergic cough.

    • Etiology

    Causes

    The etiology is unclear and may be related to the development of allergic diseases (e.g., eczema, urticaria, allergic rhinitis, etc.) or susceptibility to allergies.

    Triggering factors

    It is easily triggered by oil smoke, dust, cold air and speech.

    Symptoms

    Main Symptoms

  • Cough: mostly paroxysmal, irritating dry cough, which can occur during the day or at night.
  • Pharyngeal discomfort: often accompanied by tickling in the throat.

    • Consultation

    Department of Medicine

    Respiratory Medicine

    If the irritating dry cough does not subside, prompt medical attention is recommended.

    Preparation

    Preparation for medical consultation: registration, preparation of documents, FAQs

    Tips

  • Avoid taking cough suppressants on your own before going to the doctor to avoid influencing the doctor’s judgment of the condition.
  • Chest X-ray or chest CT is often needed, so avoid wearing clothes made of metal. Those who are pregnant or planning to be pregnant should inform the doctor.

    • Preparation Checklist

    症状清单

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

  • Is there fever? What is the highest degree?
  • Is there a cough? How long has the cough lasted?
  • Is there any sputum? What kind of phlegm?
  • Is there nasal congestion or runny nose?
  • How long have the symptoms been present?
  • Under what circumstances do the symptoms worsen or lessen?
    • 病史清单
  • Have you had a cold or been overworked recently?
  • Are there any allergic foods, medications, etc.?
    • 检查清单

    Test results in the last 6 months to bring to the doctor

  • Laboratory tests: blood test, C-reactive protein, specific IgE test, induced sputum cytology
  • Imaging tests: chest X-ray, chest CT scan
  • Pulmonary function tests: pulmonary ventilation function test, bronchial provocation test
    • 用药清单

    Medication use in the last 3 months, bring the box or package with you to the doctor’s office if available

  • Glucocorticoids: budesonide aerosol, methylprednisolone
  • Antihistamines: loratadine, cetirizine
  • Cough suppressants: codeine, dextromethorphan

    • Diagnosis

    Diagnosis is based on

    Medical history

    History of allergic diseases or exposure to allergic substances.

    Clinical manifestations

    症状
  • Cough: paroxysmal, irritating dry cough that may occur both during the day and at night. Cough is easily induced by fumes, dust, cold air, and speech.
  • Pharyngeal discomfort: often accompanied by tickling of the throat.
    • 体征

    Most often there are no abnormal physical signs. Lung auscultation may help to rule out bronchial asthma, etc.

    Laboratory tests

    呼出气一氧化氮（FeNO）水平检查
  • Noninvasive airway inflammation screening techniques developed in recent years.
  • Increased FeNO levels (>32 ppb) suggest eosinophilic inflammation or hormone-sensitive cough is likely.
    • 血清抗体检查
  • Serum antibodies such as immunoglobulin E (IgE) tests can help in the diagnosis of allergic cough by knowing whether the patient has atopic constitution.
  • Atopic constitution is present in 60% to 70% of cough variant asthma and 30% of eosinophilic bronchitis and needs to be differentiated.
    • 血常规检查

    Elevated peripheral blood eosinophils are suggestive (> 300/μl) of atopic disease, and significant elevation (> 20%) is suggestive of parasitic infections, eosinophilic pneumonitis, and others.

    诱导痰细胞学检查
  • The most important non-invasive test for diagnosing the etiology of chronic cough and airway inflammation, safe and well tolerated.
  • In patients with allergic cough, induced sputum eosinophils are not high.

    • Imaging

  • It is primarily a rule-out test.
  • There are no obvious lesions on chest X-ray. If there are suspicious lesions and other diseases are suspected, the doctor will arrange chest CT or high-resolution CT.

    • Lung function tests

  • It mainly includes pulmonary ventilation function test and bronchial provocation test, which are routine tests for chronic cough.
  • Hospitals that are not equipped to perform bronchial provocation test may also monitor the peak expiratory flow rate variability (PEFR), mainly to exclude cough variant asthma.

    • Other Tests

  • Bronchoscopy is not routinely performed for chronic cough, but may be used to rule out cough due to airway pathology, such as bronchopulmonary cancer, foreign bodies, and tuberculosis.
  • Allergen skin test can help determine the type of allergen.

    • Diagnostic Criteria

    China’s 2015 edition of the Guidelines for the Diagnosis and Treatment of Cough suggests that a diagnosis of allergic cough can be made if the following criteria are met

  • Chronic cough, ≥8 weeks in adults and ≥4 weeks in children, mostly irritating dry cough.
  • Normal pulmonary ventilation and negative bronchial provocation test.
  • Induced sputum eosinophils are not high.
  • One of the following indications: history of allergic disease or allergic substance exposure; positive allergen skin test; elevated serum total immunoglobulin E (IgE) or specific IgE.
  • Effective treatment with antihistamines and/or glucocorticoids.

    • Differential Diagnosis.

    The disease needs to be differentiated from cough variant asthma (CVA), eosinophilic bronchitis (EB), and bronchial asthma.

    DiseaseAllergic coughCough variant asthmaEosinophilic bronchitisBronchial asthmaSymptoms only cough only cough cough, cough chest tightness, cough, cough, sputum, dyspnea, etc.SymptomsCough onlyCough onlyCough, coughing up phlegmChest tightness, cough, sputum, dyspnea, etc.Allergy Signs Common Common Common Same as General Population Common

    Allergies

    Common

    Common

    Same as general population

    Common

  • Respiratory HyperreactivityNoNoNo
  • Respiratory hyperreactivity
  • No

    • No

    No

    Yes

    Sputum eosinophilia visible visible very common visible

    Eosinophilia in sputum

    Visible

    Visible

    Very common

  • Visible
  • Bronchoscopic biopsy eosinophilia common common very common common
  • Bronchoscopic biopsy eosinophilia
  • Common

    • Very common

  • Very common
  • Very common
  • Bronchodilator reactionNoNoNoNo
  • Bronchodilator reaction
  • No
  • Yes, yes, yes

    • No

    Yes

  • Good sensitivity to glucocorticoids
  • Response to glucocorticoids
  • Good
  • Good
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