Both common cold and allergic rhinitis (AR) are common and frequent diseases in children. Most children have 3-8 common colds per year, and 10%-15% of them have up to 12. The prevalence of AR among children in China is about 7.83%-20.42%. Common cold is mostly an acute inflammation of the nose and pharynx caused by viral infection, while AR is a nasal disease triggered by allergen stimulation. The two diseases often show similar nasal symptoms, including runny nose, nasal congestion and sneezing, etc., and 44%-87% of children with rhinitis may have mixed rhinitis. Meanwhile, the common cold can exacerbate the symptoms of AR or trigger an acute attack of AR, and atopic children are susceptible to the common cold, so the two diseases are often confused. In addition, the clinical manifestations of AR in children are different from those in adults, such as a higher proportion of cough symptoms (69.8% in preschool children and 38.1% in school-age children), which makes it more difficult to recognize the common cold and AR in children. There is a gap in clinicians’ knowledge of the common cold, with duplication of medications, inappropriate combinations of medications, and misuse of antimicrobials and antivirals. Due to the special characteristics of children’s physique, untimely treatment of common cold and AR can lead to complications such as sinusitis, otitis media, bronchitis, etc. Therefore, it is of great significance to recognize and treat children’s common cold and AR at an early stage. 1 Etiology and pathogenesis From the perspective of pathogenesis, children’s common cold and AR are both local and systemic inflammatory reactions of nasal mucosa caused by external stimuli (viruses, allergens, etc.) and immune cells, and the main inflammatory mediators involved include histamine, kallikrein, and leukotrienes. 1.1 Common cold, i.e. acute infectious rhinitis and pharyngitis, is the most common type of upper respiratory tract infection, with viral infections, of which rhinoviruses are the most common (30%~50%), followed by coronaviruses, respiratory syncytial viruses, parainfluenza viruses and so on, and can also be combined with bacterial infections. When the virus reaches the nose and pharynx, it combines with the epithelial cells and replicates in the epithelial cells and local lymphoid tissues, causing the release of inflammatory mediators such as kinin, histamine, leukotrienes, etc., which leads to an increase in vascular permeability, plasma exudation, and an increase in glandular secretion. Children with atopic constitution are prone to common cold. 1.2 Allergic rhinitis AR is a non-infectious inflammatory disease mediated by IgE after exposure of the organism to allergens. When the sensitized nasal mucosa is exposed to the same allergen again, the combination of allergen and IgE activates mast cells and basophils, causing the release of inflammatory mediators such as histamine, leukotrienes, and kallikrein, which stimulate the sensory nerve endings and blood vessels of the nasal mucosa and produce symptoms such as watery runny nose, itchy nose, and sneezing, etc. This process is a rapid-onset phase reaction. The above inflammatory mediators can also induce the expression and secretion of adhesion molecules, chemokines and cytokines, leading to the further release of leukotrienes, prostaglandins, platelet-activating factor, etc., which aggravates the inflammatory reaction of the nasal mucosa, resulting in obvious tissue edema leading to nasal congestion, which is a delayed-phase response.The pathogenesis of AR is associated with the interactions of heredity and the environment, and the incidence rate of AR has significantly risen in China in the past two decades. 2.1 Common cold 2.1 Common cold often occurs at the time of seasonal change and winter and spring, the onset of the disease is more acute, the early main manifestations of the nose, pharyngeal symptoms, sneezing, nasal congestion, watery nasal discharge, sore throat and other symptoms, starting 10 to 12 hours after infection, 2 to 3 days to reach the peak, and then gradually reduce the duration of 7 to 10 days, and some of the children can last up to 3 weeks or even longer. Elderly children may complain of itching, sore throat and burning sensation in the pharynx, with mild systemic symptoms. Fever is unremarkable or low. Infants and young children tend to have unremarkable nasal and pharyngeal catarrhal symptoms and more severe systemic symptoms, which may start suddenly with a sudden onset of high fever, loss of appetite, followed by sneezing, runny nose, and cough. Physical examination reveals nasal mucosal congestion, edema, watery secretions, mild pharyngeal congestion, and no abnormalities on chest examination. 2.2 Allergic rhinitis (AR) is mainly characterized by watery nasal discharge, nasal itching, nasal congestion, sneezing and other symptoms, which may be accompanied by ocular symptoms such as eye itching and conjunctival congestion. Some children may have “allergic salute”, i.e., rubbing the nose upward with the palm of the hand or fingers in order to alleviate nasal itching or improve nasal ventilation. Physical examination shows that the nasal mucosa is pale and edematous, and the nasal mucus is clear and watery. Some children may have: (1) allergic dark circles under the eyes, which appear as dark shadows on the lower eyelids due to swelling of the lower eyelids; (2) allergic wrinkles, which appear as transverse wrinkles on the skin of the nose due to frequent upward rubbing of the nasal tip. Children with asthma, eczema, or atopic dermatitis have corresponding pulmonary and skin signs. AR was categorized as intermittent or persistent based on symptom duration: intermittent symptom presentation <4 days/week or continuous <4 weeks; and vice versa for persistence. According to the severity of symptoms, it can be categorized as mild AR and moderately severe AR: mild does not interfere with sleep, daily activities, and study, and has no bothersome symptoms; if more than one of them is affected, it is moderately severe. Mild, intermittent AR is clinically similar to the common cold and is more difficult to distinguish. The onset of symptoms in seasonal AR is seasonal, and the duration of seasonal allergen exposure in different regions is influenced by factors such as geography and climatic conditions. 3.1 Diagnosis and differential diagnosis 3.1 Common cold The diagnosis of common cold is mainly based on clinical symptoms and signs, but other diseases must be ruled out. The symptoms of the prodromal stage of many infectious diseases in children are similar to common cold, such as measles, epidemic cerebrospinal meningitis, whooping cough, scarlet fever, polio, encephalitis B, hand-foot-and-mouth disease, etc., which should be analyzed comprehensively with the epidemiological history of infectious diseases, contact history, symptoms, signs and laboratory data, and closely observe the symptoms. The information should be analyzed in conjunction with the epidemiological history of the infectious disease, history of exposure, symptoms, signs and laboratory data, and the evolution of the disease should be closely observed for identification. In laboratory tests, the peripheral blood leukocyte count of viral infections is normal or low, the proportion of lymphocytes is relatively increased, and the leukocyte and lymphocyte counts of some children are decreased. Some children have decreased white blood cell counts and lymphocyte counts. Those with bacterial infections have increased peripheral blood leukocyte counts and neutrophil counts, which may be accompanied by increased acute-phase reactive indexes such as C-reactive protein. 3.2 Allergic rhinitis AR should be diagnosed on the basis of the child's typical allergic history, clinical presentation, and consistent allergen test results. The diagnosis of AR in children can be confirmed with one of the symptoms of nasal congestion, nasal overflow, nasal itching, sneezing, clear watery runny nose, oedema and pallor of the nasal mucosa, redness of the eyes, and tearing, as well as a positive result of any one of the two items of the skin prick test or the serum-specific IgE test. 3.3 Differential diagnosis between the common cold and AR The key points of the differential diagnosis of the common cold and AR are shown in Table 1. Consider the possibility of AR in the following situations It is recommended to transfer to ENT department for treatment: ① sneezing and runny nose for more than 2 weeks, and after symptomatic treatment of common cold, the nasal symptoms do not get better, or even aggravate or recurring; ② typical nasal symptoms, with obvious triggers, and fixed time-phase episodes; ③ the child is accompanied by conjunctivitis, asthma, and eczema, then AR is more likely to be present. Skin prick test and serum-specific IgE test are helpful for clinical identification, but they have their own advantages and disadvantages. ① Skin prick test sensitivity and specificity of allergens can reach more than 80%, the disadvantage is that it will be affected by the patient's medication, which may cause systemic allergic reactions; ② serum-specific IgE test will not cause systemic allergic reactions, is not affected by the patient's medication, and it can be applied to the skin when there is a lesion, the disadvantage is that it may be subject to laboratory errors. 4 Treatment For children with a clear diagnosis of common cold and AR, treatment can be provided according to the guidelines or consensus for the diagnosis and treatment of the respective diseases. If the diagnosis is unclear, empirical diagnosis and treatment can be carried out according to the following procedure. 4.1 Empirical diagnosis and treatment Theoretically, the identification of common cold and AR can be based on typical clinical manifestations and allergen testing, but since the nasal symptoms of the two diseases are similar in the early stage of the disease and there is no obvious difference in the signs, and some hospitals do not have otorhinolaryngology and allergen testing equipment, the two diseases are not easy to be identified in the clinic, and misdiagnosis and underdiagnosis are more common. Therefore, under the premise of excluding other diseases with symptoms of upper respiratory tract infections, symptomatic treatment can be adopted to control symptoms such as nasal congestion and runny nose and prevent complications in cases where it is not possible to clearly distinguish between common cold and AR. It is recommended that one or more drugs may be selected for combination therapy depending on the severity and severity of the child's symptoms. The empirical diagnostic and treatment process of children's common cold and AR is shown in Figure 1. In the early stage of the disease, if nasal congestion, sneezing, and runny nose are the main manifestations, but not accompanied by fever, and if the symptoms are obvious, oral decongestants can be used in conjunction with oral or nasal antihistamines for symptomatic treatment; combined with the symptoms of coughing, cough expectorant medication can be added, and compounded cold and flu preparations that don't include antipyretic and analgesic medication can also be used. Empirical treatment and observation for 5~7 days with symptomatic relief support the diagnosis of common cold; if the symptomatic relief is not obvious or the symptoms recur after stopping the medication, the possibility of AR should be considered, and it is recommended to refer to otorhinolaryngology specialists. For atopic children with a history of asthma, eczema or atopic dermatitis, or children who have been diagnosed with AR, if nasal congestion, sneezing, runny symptoms, but not accompanied by fever, can be treated symptomatically according to AR, plus nasal hormones combined with oral or nasal antihistamines; coughing, if accompanied by symptoms of the lower respiratory tract (airway hyperresponsiveness, bronchial asthma, etc.) In addition to symptomatic treatment, the addition of anti-leukotriene drugs. Children with early nasal congestion, sneezing, runny nose as the main manifestations, and accompanied by fever, sore throat and other systemic symptoms, the first consideration of the common cold, can be given to oral decongestant combined with oral or nasal antihistamines, as well as antipyretic medication for symptomatic treatment; combined with coughing symptoms can be added to cough expectorant drugs, but also can be used to contain antipyretic drugs of the combination of cold and flu preparations. If the symptoms are relieved in 3~5 days, the diagnosis is clear; if the symptoms of fever and sore throat are relieved after treatment, but the symptoms of nasal congestion and runny nose last for more than 10~14 days, it should be noted that there is a possibility of AR or mixed rhinitis, and it is recommended to refer to the otorhinolaryngology specialists. 4.2 Commonly used therapeutic drugs for rhinitis Antihistamines: through blocking histamine receptors to inhibit the dilatation of small blood vessels, reduce vascular permeability, eliminate or reduce the symptoms of sneezing and runny nose in patients with AR and common cold, which can be categorized into nasal and oral. children with AR are recommended to use the second generation of antihistamine drugs and above. Oral antihistamines are effective for runny nose, sneezing, itchy nose and eye symptoms, and less effective for nasal congestion. Nasal antihistamines have high concentration at the site of administration, fast onset of action, and small systemic reaction, especially for children, and can relieve itchy nose, sneezing, and runny nose, but are ineffective for eye symptoms. Decongestants: by activating β-adrenergic receptors and producing vasoconstriction effect on nasal mucosa, they can quickly relieve symptoms of nasal congestion caused by common cold or AR. However, it should not be applied continuously for more than 7 days and is not effective for symptoms such as nasal itching, sneezing and runny nose, so it is more effective to combine it with other drugs such as oral antihistamines. Nasal glucocorticoids: can significantly relieve nasal symptoms caused by rhinitis such as nasal congestion, runny nose, nasal itching, sneezing, etc. The relief of symptoms is better than that of other drugs, but the onset of effect is slower, usually within 36h after the first dose is given, and in the following days, the symptoms are significantly improved. Children of different ages should be used as recommended in the instructions for each type of medication. For prolonged use of nasal glucocorticoids in children, the minimum effective dose should be used and physical development should be monitored regularly. Leukotriene receptor antagonists: Selectively bind to the cysteinyl leukotriene receptor (CysLT1) and exert a therapeutic effect by competitively blocking the biological action of cysteinyl leukotrienes. Oral leukotriene receptor antagonists are first-line therapeutic agents for AR, providing effective relief of sneezing and runny symptoms, and can be used clinically for the treatment of AR with or without asthma. Combinations: Combinations are recommended for patients who do not respond well to monotherapy. Oral antihistamines + oral decongestants are more effective than oral antihistamines or decongestants alone; nasal antihistamines + nasal glucocorticoids are more effective than nasal antihistamines or glucocorticoids alone. Meta-analysis showed that the combination of oral leukotriene receptor antagonists and antihistamines significantly improved symptom scores in patients with seasonal AR better than monotherapy, and leukotriene receptor antagonists combined with nasal glucocorticoids were more efficacious than nasal glucocorticoids alone.