OVERVIEW

What is allergic cough?

Allergic cough refers to chronic coughing in certain patients with allergic constitutions after exposure to triggering factors (such as seasonal pollen or air pollution) or non-allergenic substances that irritate the bronchial mucosa. Symptoms can be effectively relieved with glucocorticoids and antihistamines^[1].

Currently, there is no international diagnostic standard for allergic cough. Due to its distinct clinical features compared to typical bronchial asthma and non-asthmatic eosinophilic bronchitis, it is considered an independent type of cough.

The main risk factors for clinical onset include cooking fumes, cold air, air pollution, excessive talking, and a history of other allergies. The primary clinical characteristic of allergic cough is long-term paroxysmal, irritating dry cough accompanied by throat itching, which can occur at any time but is most noticeable at night or in the morning, severely disrupting daily life^[2].

If allergic cough is not treated promptly and effectively, it may lead to complications such as urinary incontinence. If chronic cough persists after exposure to allergens without improvement, early diagnosis and treatment are necessary.

Doctors will carefully inquire about clinical symptoms and allergen exposure history, conduct a comprehensive respiratory examination, and make a clinical diagnosis based on imaging (X-ray, CT), pulmonary function tests (ventilation function, bronchial provocation test), and laboratory results.

Medication is the primary treatment for allergic cough, with glucocorticoids or antihistamines being effective. Patients should avoid known allergens and may manage symptoms at home during flare-ups^[3].

Is allergic cough common?

Clinically, there are many patients with chronic cough, especially among children. Allergic cough accounts for 13% of chronic cough cases in children, meaning 13 out of 100 children with chronic cough have allergic cough^[4].

Are allergic cough and cough-variant asthma the same condition?

No.

Allergic cough is not a formal clinical diagnosis and cannot be equated with cough-variant asthma. According to respiratory consensus, allergic cough is a broad concept referring to a type of cough triggered by allergen exposure but with normal eosinophil levels in sputum and no airway hyperresponsiveness. In contrast, cough-variant asthma features normal lung ventilation but significantly increased airway responsiveness. The cough may persist for over 4 weeks, often occurring at night and/or in the early morning, triggered by exercise or cold air. It shows no signs of infection or responds poorly to antibiotics but improves significantly with bronchodilators.

Which department should I visit for allergic cough?

Respiratory department or allergy (allergology) department.

SYMPTOMS

What are the symptoms of allergic cough?

The main clinical features of allergic cough include^[5]:

• Chronic cough, usually lasting more than one month;
• Paroxysmal, irritating dry cough, which can occur during the day or night and may worsen after exercise or inhalation of cold air;
• Often accompanied by throat itching or a foreign body sensation;
• No fever, no purulent nasal discharge or sputum, and no obvious signs of infection.

What other diseases can allergic cough cause?

If allergic cough is not treated promptly and effectively, it may lead to the following complications^[6]:

• Mechanical damage to the tracheal mucosa: Persistent coughing can cause bronchial inflammation, leading to damage of the bronchial mucosa, and may also result in dizziness and shortness of breath.
• Urinary incontinence: Increased abdominal pressure due to persistent coughing may cause uncontrolled urine leakage.

CAUSES

What causes allergic cough?

Allergic cough, also known as atopic cough, is not currently a widely recognized independent disease diagnosis internationally. It is a concept used primarily in certain countries, particularly in East Asia (e.g., Japan), in clinical research and practice. Chronic cough refers to a condition where coughing is the main symptom, lasting for more than 8 weeks, with no significant abnormalities on chest X-rays or lung CT scans. Allergic cough is a major type of chronic cough in East Asian patients, accounting for about 10–15%^[8,9].

The pathogenesis of allergic cough remains unclear, but possible causes include:

• Patients may have an allergic predisposition, and exposure to allergens triggers an allergic reaction, leading to airway inflammation and increased sensitivity of the cough reflex.
• Some studies suggest that fungi may be one of the allergens responsible for allergic cough^[10].
• Cooking fumes, dust, cold air, or excessive talking can also easily induce coughing, often accompanied by throat itching^[11].

Allergic cough differs from cough-variant asthma. The mechanism of allergic cough primarily involves heightened cough sensitivity, meaning the cough trigger is particularly sensitive to specific allergens, making coughing more likely. In contrast, cough-variant asthma involves airway hyperresponsiveness, where the airways constrict and become inflamed upon exposure to allergens, leading to coughing. Laboratory tests show that patients with allergic cough have normal sputum eosinophil counts and unaffected lung function^[10,11].

What are the high-risk factors for allergic cough?

• Cooking fumes;
• Cold air;
• Dust or air pollution;
• Irritant gases;
• Seasonal pollen or airborne particles;
• Excessive talking;
• Other allergic conditions.

Is allergic cough contagious?

Allergic cough is not contagious.

Is allergic cough hereditary?

Allergic cough may be hereditary because the primary cause is an allergic constitution, which is generally associated with a family history of allergies^[4].

DIAGNOSIS

How do doctors diagnose allergic cough?

Doctors can make a preliminary clinical diagnosis by carefully inquiring about the patient's clinical symptoms and history of allergen exposure, along with a comprehensive examination of the respiratory system. Generally, the following types of tests are required^[3]:

• Imaging tests: X-ray or CT scans of the chest are used to assess lung damage and evaluate the severity of the condition.
• Pulmonary function tests: Spirometry checks whether lung ventilation is normal, often used to differentiate from asthma; bronchial provocation tests evaluate lung indicators, with allergic cough typically showing negative results.
• Sputum cytology test: This non-invasive test examines inflammatory cells in the patient's sputum to distinguish conditions like eosinophilic bronchitis and asthma, offering good safety and tolerability.
• Allergen testing: Usually conducted early in the disease course to identify allergens, allowing targeted preventive and therapeutic measures.

What diseases should allergic cough be differentiated from?

Many conditions share similar symptoms with allergic cough, including cough-variant asthma, upper airway cough syndrome, eosinophilic bronchitis, gastroesophageal reflux-induced cough, drug-induced cough, and post-infectious cough. Therefore, for patients with chronic or recurrent cough unresponsive to antibiotics, accurate differentiation and diagnosis of allergic cough are essential^[3].

TREATMENT

What are the treatment options for allergic cough?

Doctors need to select different treatment plans based on the severity of the patient's condition. Drug therapy is the primary treatment for allergic cough. Clinically, inhaled corticosteroids or oral glucocorticoids are commonly used, which are effective. These are often combined with bronchodilators and antihistamines. In the early stages of the disease, if symptoms are mild, inhaled corticosteroids and antihistamines may be administered via nebulization^[3,7].

• Glucocorticoids: If symptoms are severe, inhaled glucocorticoids (such as budesonide or fluticasone) may be used for more than 4 weeks, or short-term oral glucocorticoids (3–5 days) until symptoms are completely relieved. Compared to oral glucocorticoids, inhaled corticosteroids have fewer side effects but may cause hoarseness or throat discomfort. It is recommended to rinse the mouth after inhalation to reduce the risk of fungal infections.
• Antihistamines: Such as loratadine, desloratadine, or cetirizine tablets. Alcohol should be avoided during use, as it may cause dizziness, drowsiness, or other adverse reactions. Drivers or those working at heights should use them with caution.
• Since bacterial infection is not involved, doctors generally do not prescribe antibiotics.

When should you seek medical attention for allergic cough?

If a patient develops chronic cough after exposure to allergens and the condition does not improve, early diagnosis and treatment are necessary. Since various types of cough can be triggered by common allergens, the condition must first be clarified. Based on the diagnosis, the doctor can then develop an appropriate treatment plan for targeted therapy.

DIET & LIFESTYLE

What should patients with allergic cough pay attention to in daily life?

Patients should avoid exposure to all known allergens and may perform home treatments to relieve symptoms during flare-ups^[4]:

• Inhaling heated steam may help alleviate symptoms of allergic cough, but ensure safety to avoid burns;
• When going out, strengthen personal protection and avoid contact with all known allergens;
• Use air purifiers and humidifiers indoors, maintain cleanliness, and ventilate frequently. Wash clothes and bedding regularly and expose them to sunlight to prevent dust mite allergies.
• During sudden temperature drops in winter or severe air pollution, keep warm and minimize outdoor activities. Reduce outings during allergy-prone seasons, wear masks, and avoid pollen-induced allergies.
• Wash your face after returning from outside and clean your nasal passages daily.

What dietary precautions should patients with allergic cough take?

Avoid consuming known allergenic foods. When uncertain, be cautious with common allergens such as seafood (shrimp, crab), peanuts, and milk.

Avoid alcohol and foods high in salt or spice to prevent respiratory irritation and worsening of symptoms.

PREVENTION

Can Allergic Cough Be Prevented?

The mechanism of allergic cough is related to genetic defects or immune dysfunction, and allergens are complex and diverse, making complete prevention often difficult.

Clinically, it is impossible to prevent an individual from developing an allergic reaction to a specific allergen or to predict the allergen before the first allergic episode occurs. Even after an allergic cough develops, identifying the exact allergen may remain challenging.

However, patients can take preventive measures during high-risk seasons to potentially reduce the likelihood of an attack:

• Allergic cough is often linked to inhaled allergens such as dust mites, mold, and pollen. Once identified, strict avoidance is necessary.
• Avoid secondhand smoke and strong odors, limit overly sweet, salty, or spicy foods, and monitor symptoms at home with a peak flow meter if possible^[4].