ABPA was reported in 1952 by Hinson et al. [61] who described three patients who were diagnosed with pulmonary infiltrates and eosinophilia in blood and sputum. It was clinically proven that these symptoms occur when patients are suffering from severe asthma. But for ABPA, there are no specific physical or chemical examination findings at present to diagnose on the basis of symptoms like cough, wheezing, shortness of breath with fever, anorexia, and malaise. ABPA can be identified by local and IgE circulating specific Aspergillus antibodies and skin tests with reactive Aspergillus, eosinophilia, increased interleukin-2 (IL-2) level, and increased serum IgE level [51]. It includes new lung infiltrates or bronchiectasis on chest imaging. Pathologically, ABPA is characterized by one or more of the conditions like mucoid impaction of bronchi, bronchocentric granulomatosis, eosinophilic pneumonia, and exudative or obliterative bronchiolitis [43, 60].

Bronchial asthma is diagnosed using a specific skin test in IgE levels for Aspergillus antigens. If the IgE levels are below 1,000 IU/mL, high resolution computer tomography (HRCT) test is conducted to observe mild-to-severe asthma which is further diagnosed using Asthma and Allergy Foundation of America (AAFS) where a positive test suggests mild-to-moderate asthma while the SAFS-positive test indicates severe asthma. When HRCT-complete blood count (CBC) is negative then invasive bronchial-pulmonary aspergillosis (IBPA) is conducted to confirm negative asthma; if HRCT-CBC is positive than ABPA-CBC is performed for confirmation [54, 62].

Intestinal microbiota that is “healthy gut” promotes the rate of immunity [17, 31]. Gut-associated lymphoid tissue (GALT), which includes Peyer’s patches, has been shown in other investigations to be underdeveloped or missing in germ-free mice [82, 83]. It was revealed that the redevelopment of GALT and the induction of tolerance may result from the neonatal administration of Bacteroides fragilis to germ-free mice’s lower gut [84]. It is also established that the host’s risk of contracting allergy and inflammatory disorders increases if an effective immunological tolerance cannot be developed early in life [85]. For instance, mice raised in sterile environments have fewer Treg cells that produce IL-10 and IgA, and they are unable to acquire oral antigenic tolerance [17, 85–87]. The several factors that influence the advantages of probiotic supplementation include a system for action. Maldonado Galdeano et al. [88] recently examined probiotics’ advantages for people. Oral probiotics interact with the body after administration via TLRs, intestinal epithelial cells (IECs), and immune-competent cells [89]. The creation of mediators, cytokines, and chemokines is encouraged by this interaction. The activation of mucosal immunity is caused, in part, by macrophage chemo-attractant protein 1, which is secreted by IECs and is sustained by an increase in mucosal tissues’ IgA-secreting cells [90, 91].

Filamentous bacteria with segments, specifically clusters IV and XIVa, support the growth of Treg cells and IL-17-producing T cells, respectively [90–92]. Additionally, food’s gut microbiome, when put into germ-free mice and allergic mice but not tolerant ones, transmitted susceptibility to food allergy [69]. The examination of dysbiosis in people with food allergies is complicated by a number of circumstances. Because of the variety in study design, sample size, age at fecal collection, methods of gut microbiome analysis, and geographical location, comparisons between studies are challenging [93]. Nevertheless, with time and the increasing accessibility of new tools, the evidence of gut dysbiosis in food allergy is growing. Babies with cow’s milk allergies had higher total bacterial and anaerobic counts as revealed in bacterial cultures [94], numerous hypothesized mechanisms have been proposed to explain how the commensal microbiota affects the course of the allergic reaction [95]. Through their TLRs, intestinal bacteria can directly affect Tregs, modulating innate lymphoid cells. By means of a Treg intrinsic, TLR and myeloid differentiation primary response gene 88 (MyD88) reliant mechanisms and commensal microbiota support the differentiation of induced Tregs (iTreg) from naive clusters of differentiation-4 (CD4⁺) T-cells [96, 97].

There are a number of Lactobacillus species that are helpful in the treatment of respiratory allergies such as L. reuteri, L. casei, L. rhamnosus, L. acidophilus, L. plantarum, B. lactis, and Bifidobacterium longum. L. reuteri modification caused pro-inflammatory cytokines like IL-5 and IL-13 to be produced at lower levels and the outcome is a reduction in the influx of inflammatory cells to the lungs (Figure 4). L. casei helps in dendritic cell (DC)-specific intercellular adhesion molecule 3-grabbing non-integrin modulates DC activity in vitro after the induction of Tregs that produce IL-10 in vitro. Increased L. rhamnosus and B. lactis transforming growth factor-β (TGF-β) in vivo expression is connected with the induction of Tregs that prevent allergic sensitization and airway illness in mouse models of asthma [62]. L. rhamnosus and Bifidobacterium decrease persistent chronic allergic inflammation through upregulation of TLR4 and messenger RNA (mRNA) expression, which helps in airway remodeling, mast cell degranulation inhibition, and suppression of pulmonary airway inflammation. L. acidophillus stimulates DCs in vitro and this increases TGF-β production. L. plantarum regulates high concentrations of specific IgG2a, inhibits the specific IgE response, and enhances interferon-gamma (IFN-γ) production [98].

T cells are also triggered by probiotics. Additionally, probiotics encourage the release of IL-10, the primary regulatory and anti-inflammatory cytokine from Treg cells [99]. Probiotics also strengthen the intestinal barrier by boosting mucins, tight junction molecules, goblet and Paneth cells. Probiotics regulate the gut microbiota by maintaining homeostasis and preventing the spread of infections, among other things [100]. Additionally, probiotics’ viability is essential to guarantee their impact on innate immunity [101]. Probiotics may therefore be an intriguing natural method for both prevention and treatment. By decreasing IgE production and boosting the immune response to combat infections, they could increase type-1 response [102, 103]. SCFAs, which are produced by bacterial fermentation of food fibers, are another way in which the commensal flora encourages tolerance. By increasing colonic Treg cells, SCFA protects mice from intestinal inflammation by acting on T cells through the G-protein-coupled receptor 43 (GPR43). Intestinal Treg cells can be produced from naive CD4⁺ T cells by T-cell intrinsic epigenetic pathways, which is another benefit of SCFAs [104]. With increased forkhead box protein 3 (Foxp3) protein acetylation, butyrate, an SCFA recognized as a histone deacetylase inhibitor, confers higher stability and enhanced suppressive action on de novo-produced intestinal iTreg cells [105]. A high-fiber diet reduces allergic airway inflammation by changing the flora’s composition, which increases Bacteroidetes and decreases Firmicutes while raising the amounts of SCFAs in the bloodstream [106].

In general, preventive strategies are [107]:

(1)

Prevention of exposure to tobacco smoking during pregnancy and after delivery is a general health education message.

Pre-clinical research has demonstrated that altering the microbiota can influence the host’s overall immune response, hence lowering allergy inflammation and sensitization shown in Figure 5 [108, 109]. Numerous researches have raised the possibility that pre- and probiotics could provide protection against asthma [65, 67, 74, 79, 89].

When allergens are inhaled, the innate immune system is stimulated to release cytokines that help CD4⁺ T cells express and recognize antigens and activate T cells and antigen-presenting cells to induce Th2 responses [110, 111]. Th2 cytokines (IL-4, IL-5, IL-9, and IL-13) cause eosinophilia in the airways, pulmonary lymphocytosis, mastocytosis, alternative macrophage activation, and epithelial cell proliferation with goblet cell hyperplasia, which are alterations that resemble asthma in the airways and lung parenchyma. A number of inflammatory disorders have been linked to matrix metalloproteinases (MMPs), a family of enzymes that cleaves extracellular matrix proteins [84]. MMP9 levels are specifically markedly elevated in asthma [112]. It has also been demonstrated that administration of Lactobacillus rhamnosus GG (LGG) reduces MMP9 expression in lung tissue and prevents inflammatory cell infiltration. In addition, in OVA-sensitized mice, LGG decreased blood levels of OVA-specific IgE, inhibited methacholine-induced AHR, and decreased the quantity of infiltrating inflammatory cells and Th2 cytokines in both serum and bronchoalveolar lavage fluid [113]. Other probiotics have yielded comparable outcomes [114]. Particularly in children with paediatric asthma, LGG was found to lower the level of exhaled nitric oxide in 4- to 7-year-olds [115], however, it was unable to duplicate these findings [116]. Early administration of Lactobacillus reuteri, Lactobacillus rhamnosus HN001, or Lactobacillus paracasei species paracasei F19 did not reduce asthma [respiratory rate (RR) 1.16; 95% confidence interval (CI) 0.33–4.10], and neither did Lactobacillus paracasei species paracasei F19 (RR 1.05; 95% CI 0.39–2.81) [117–119].

Based on the in vitro manipulation of cytokine production, probiotic bacteria have produced better effects. It has been demonstrated that Bifidobacterium bifidum, B. lactis, and Lc. lactis can effectively induce IL-10 and significantly suppress the Th2-related cytokines IL-5 and IL-13 [120]. Administered perinatally in a selected combination, they reduced the development of eczema up to the age of 2 years. Their beneficial effect does not reach the age of 6 years and does not lead to primary prevention of asthma. A systematic review of randomized trials assessing the effects of any probiotic administered to pregnant women, breastfeeding mothers, or infants demonstrated that probiotics could reduce the risk of eczema in infants [121]. Due to the possibility of bias, the inconsistent and imprecise nature of the results, and the indirect nature of the available research, the certainty of the evidence is low or extremely low. Replication of the encouraging findings in collaborative, well-coordinated multicenter harmonized studies with multidisciplinary expertise in paediatrics, immunology, and microbiology would, therefore, be of utmost significance to enable future evidence-based implementation, as emphasized in two recent reviews [122]. A longer-term effect from gut microbiota control is possible [123, 124].

There have been numerous randomized placebo-controlled trials to look at the possibilities of oral probiotic administration in conditions affecting the upper respiratory system [132, 133]. In a meta-analysis by Peng et al. [134], probiotic effectiveness for the prevention and/or treatment of AR was examined in 11 randomized controlled trials. Results indicated that probiotic medication improved the patients’ quality of life and nasal symptoms in these 11 trials. However, none of the probiotic approaches examined could lessen the inflammatory markers in these people or stop AR [135]. Most recently, in a meta-analysis by Güvenç et al. [133], 22 double-blind, randomized, and placebo-controlled studies were included, and 17 of them showed improvements in the clinical symptoms of AR patients, such as nasal obstruction, rhinorrhea, and nasal itching. In 8 of the included trials, these favorable outcomes were related to a drop in inflammatory markers [133, 135]. Patients with AR have also been investigated when multiple strains are combined. For instance, AR patients were evaluated by Hartsock and Nelson [136] on a probiotic yoghurt containing a combination of L. rhamnosus GR1 and Bifidobacterium adolescentis. Although they did not find any appreciable benefits in the participants’ clinical outcomes, they did notice elevated serum levels of IL-10 and IL-12 during the grass pollen season and elevated TGF-β during the ragweed season in the probiotic group in comparison to the placebo group 83. Therefore, after receiving probiotics, these patients’ essential regulatory indicators rose even if no changes in their symptoms were seen. The use of probiotics in patients with cytokine release syndrome (CRS) has received much less research than that for AR. In brush samples of the mucosal surfaces of the lateral, central, and medial sections of the maxillary sinuses, it was discovered that patients with CRS had less bacterial diversity and a particular depletion of helpful lactobacilli [135, 137]. Interestingly, after intranasal inoculating animals, these same scientists were able to demonstrate that Lactobacillus sakei ATCC 15521 was adequate to protect against Corynebacterium tuberculostearicum-induced sinusitis [135]. The species L. sakei was the focus of the authors’ attention since it was one of the taxa that was severely decreased in CRS patients and was present in higher abundances in the mucosa of healthy people [135]. Another multicenter, double-blind, placebo-controlled trial showed that taking Enterococcus faecalis (Symbioflor 1) for six months helped lessen the frequency of acute CRS exacerbations [137]. Furthermore, these positive outcomes persisted for 8 months following the conclusion of the therapy [135]. In agreement with these findings, Kitz et al. [138] have observed that recurrent acute sinusitis has decreased in incidence and duration. It’s interesting that these same scientists were later able to demonstrate that Lactobacillus sakei ATCC 15521 was adequate to prevent the recurrence of acute sinusitis in children who had been given oral E. faecalis Symbioflor 1 for 8 weeks [135, 138]. Additionally, previous studies investigating the use of a probiotic nasal spray for various upper respiratory tract (URT) infections, like otitis media, have already noted the safety of a probiotic spray in the nasal cavity [135, 139]. Additionally, we think that better strain selection (particularly using human isolates) from the URT may be required to detect meaningful effects on patients’ clinical symptoms [135].

Probiotics have the potential to cure chronic inflammatory URT disorders like AR and CRS, but it’s vital to keep in mind that these conditions are frequently accompanied by lower airway comorbidities, most notably, asthma [135]. Although preliminary, clinical research into the use of probiotics to treat asthma patients has produced some encouraging findings [137]. For example, Chen et al. [140] conducted a randomized, double-blind, placebo-controlled trial to examine the therapeutic efficacy of Lactobacillus gasseri PM-A0005 in asthmatic children (6–12 years old). They observed an improvement in asthma symptom scores and an improvement in airway functions, namely peak expiratory flow rates, after two months of daily treatment with 2 × 109 colony forming unit (CFU)/capsule of L. gasseri PM-A0005 [135, 140].

Moreover, they saw a considerable decline in the pro-inflammatory cytokine concentrations in the patients’ blood, including tumor necrosis factor (TNF-α, IFN-c, IL-12, and IL-13 [140]. According to these outcomes, Gutkowski et al. [141] demonstrated that giving children with mild-to-moderate atopic asthma a 12-week oral course of Trilac, a blend of Lactobacillus acidophilus, Lactobacillus delbruecki species bulgaricus, and Bifidobacterium bifidum, improved lung function and decreased asthma exacerbations. In a different trial, van de Pol et al. [142] looked at the impact of synbiotic therapy in people with asthma and dust mite allergies. In the study by Rose et al. [143], the scientists studied the effects of LGG meal supplementation over a six-month period in newborns with atopic susceptibility and recurrent wheeze. Results showed no change in clinical outcomes as determined by AD severity grading and asthma symptom score [142]. However, oral administration of LGG led to a slight reduction in aeroallergen sensitivity as a bronchial asthma predictor [143]. There has been a thorough examination of more research addressing the role of airway microbial dysbiosis in asthma and the potential of probiotics to treat these individuals [135]. These trials are encouraging, but additional study is required to determine whether or not modulating the lung microbiota by targeting the URT with nasal and/or oral probiotic therapy is effective enough.

There are insufficient pieces of evidence to recommend the use of prebiotics, probiotics, or other dietary supplements based on specific nutrients to prevent food allergy in at-risk groups and the general population, as per the European Academy of Allergy and Clinical Immunology (EAACI) food allergy and anaphylaxis guidelines on primary prevention of allergy (grade of recommendation B) [144].

After conducting a systematic literature review in 2011 on the impact of infant formula supplemented with prebiotics or probiotics on the preventive effect on allergy, the Nutrition Committee of the European Society of Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) came to the conclusion that “There is too much uncertainty to draw reliable conclusions from the available data.” [145].

The World Allergy Organization (WAO) advised considering the use of probiotics in 2015 on their guidelines for the prevention of allergy in (a) pregnant women with children who have a high risk of allergy; (b) women who breastfeed infants who have a high risk of developing allergy; and (c) infants who are at risk of developing allergies because there is a net benefit that results in primary prevention of eczema [146].

Probiotics may affect the gut microbiota and control the inflammatory response according to certain research, albeit their precise method of action in allergic illnesses is yet unknown. Given that atopic illnesses like asthma are characterized by polarized Th2 responses, it is possible to administer treatments that restore the unstable Th1/Th2 balance [147]. According to research, immune-modulatory substances, such as probiotics, can change the immune response by increasing levels of IFN-γ, a cytokine unique to the Th1 response, and lowering IL-4, a cytokine specific to the Th2 response. A few meta-analyses on the utility of probiotics in the treatment of asthma have been done recently [147]. The goal of the meta-analysis was to assess the effectiveness of probiotic supplements during pregnancy or the first few months of a child’s life for preventing AD disorders [148]. There were a total of 4,755 kids across 17 studies. Asthma and wheezing were an issue in eight investigations. Regarding asthma prevention, there was no discernible change (RR 0.99; 95% CI 0.77–1.27, P = 0.95). Additionally, comparable findings were seen in data on the advantages of probiotic usage in wheezing (RR 1.02; 95% CI 0.89–1.17, P = 0.76; fixed-effect analysis) [148, 149]. The results of the meta-analysis include the written word. Prenatal and/or early infant probiotic supplementation decreases the likelihood of atopic sensitization but may not decrease the risk of allergic reactions, according to a significant meta-analysis by Wei et al. [150]. Tang et al. [151] also discovered that there is little evidence to suggest probiotics throughout pregnancy or the first few months of a child’s life to prevent asthma in kids. The meta-analysis demonstrating the advantages of probiotic supplementation in asthmatic children was provided by Lin et al. [149]. Nine hundred and ten children from eleven studies were included in the analysis. According to the findings, kids who received probiotics had fewer asthma attacks than kids who received a placebo (RR 1.3; 95% CI 1.06–1.59). Additionally, it was shown that IFN-γ levels increased (mean differences 2.5; 95% CI 1.23–3.76) and IL-4 levels decreased (mean differences 2.34; 95% CI 3.38–1.29) [147]. The childhood asthma control test, the number of symptom-free days, the forced expiratory volume, and the peak expiratory flow did not show any statistically significant differences. The analysis’s authors acknowledge that poor enrollment in trials may have led to unsatisfactory outcomes [149].

A synthetic dipeptide called pidotimod influences both innate and adaptive immunity. It activates TLR2 and TLR4, two pattern recognition receptors (PRRs). It is widely recognized that the severity of atopic disorders correlates with PRR nucleotide polymorphisms that result in lower expression of them [147]. Pidotimod increases the release of antimicrobial peptides and enhances mucociliary transport by stimulating PRRs [153]. The use of pidotimod in treating RTIs and the related disorder obstructive syndrome (OS) has been the subject of two investigations in recent years [154–156]. Even though RTIs and OS are associated with the condition, there are actually no high-quality analyses on the effectiveness of pidotimod in treating asthma.

Similar research was done by Namazova-Baranova et al. [157] regarding pidotimod usage in kids with RTIs. Both the pidotimod-treated and placebo groups of patients were assigned. Children underwent therapy for 30 days before being monitored for 6 months.

Three time points were used to count the RTIs. The study found that the therapy program improved the rate of RTI recurrence after three months [131, 157]. Additionally, a rapid disappearance of symptoms and a quicker recovery were noted. Furthermore, pidotimod’s immune-modulatory action was demonstrated by maintaining the levels of IL-8 [131]. There is, however, a lot of hope that this medicine would improve the course of asthma because the treatment decreased the frequency of RTIs, which is closely related to asthma episodes [148].