Open Access

During the past years, there has been a global outbreak of allergic diseases, presenting a considerable medical and socioeconomical burden. A large fraction of allergic diseases is characterized by a type 2 immune response involving Th2 cells, type 2 innate lymphoid cells, eosinophils, mast cells, and M2 macrophages. Biomarkers are valuable parameters for precision medicine as they provide information on the disease endotypes, clusters, precision diagnoses, identification of therapeutic targets, and monitoring of treatment efficacies. The availability of powerful omics technologies, together with integrated data analysis and network-based approaches can help the identification of clinically useful biomarkers. These biomarkers need to be accurately quantified using robust and reproducible methods, such as reliable and point-of-care systems. Ideally, samples should be collected using quick, cost-efficient and noninvasive methods. In recent years, a plethora of research has been directed toward finding novel biomarkers of allergic diseases. Promising biomarkers of type 2 allergic diseases include sputum eosinophils, serum periostin and exhaled nitric oxide. Several other biomarkers, such as pro-inflammatory mediators, miRNAs, eicosanoid molecules, epithelial barrier integrity, and microbiota changes are useful for diagnosis and monitoring of allergic diseases and can be quantified in serum, body fluids and exhaled air. Herein, we review recent studies on biomarkers for the diagnosis and treatment of asthma, chronic urticaria, atopic dermatitis, allergic rhinitis, chronic rhinosinusitis, food allergies, anaphylaxis, drug hypersensitivity and allergen immunotherapy. In addition, we discuss COVID-19 and allergic diseases within the perspective of biomarkers and recommendations on the management of allergic and asthmatic patients during the COVID-19 pandemic.

The causative agents of respiratory allergies are bioaerosols, such as house dust mite feces, pollen grains, and fungal spores. Climate change and urbanization are considered to lead to an increase in the load of allergenic bioaerosols due to impacts on plant phenophases and allergenicity. Continuous and efficient monitoring of the atmospheric composition worldwide is essential, given the major changes involved and their impact on climate change. The complexity of the exposome, evolving from single to multiple complex exposures, is explored in this work. Acquiring information from interdisciplinary scientific disciplines, such as aerobiology (for airborne particles of biological origin), aerosol science (for airborne particles of chemical or inorganic material), and integrating this with the actual reactome of patients with respiratory diseases, we aim to provide evidence of the multifactorial nature of this interaction in real life. The objective of this review is to present how we can monitor aerosols and mostly monitor the exposome, especially the biological one, i.e., pollen and fungal spores, and what their impact is, or could be, on respiratory allergies. A huge technological advancement has been required, as traditional methods of particle collection and identification have been based on tedious laboratory procedures, with delays of more than a week. This has limited their practical use to allergic patients and their treating physicians. Automation, real-time high temporal resolution, and the use of artificial intelligence are being increasingly used in medicine. Likewise, this overview summarizes the current aerosol measurement and modeling capabilities and discusses the classification of various aerosol particles and their impact on respiratory allergies. Satellite remote sensing is highlighted as a solution to the gaps in global aerosol representation by examining aerosol load in the atmospheric column in major cities worldwide. We also discuss potential novel threats, such as pioneer bioaerosols and the respiratory epithelial barrier, as well as future insights into the impact of climate change on allergy and asthma. We conclude with a discussion of emerging co-exposures and co-diseases resulting from the ongoing climate change.