Plant-derived extracellular vesicles (PDEVs) are increasingly investigated as naturally bioactive nanovesicles and as carriers for exogenous therapeutics. Their lipids, proteins, small RNAs, and secondary metabolites can influence immune-cell function, epithelial integrity, oxidative stress, and host-microbiota interactions. However, the relevance of this evidence to allergic disease is uneven. Direct allergy-specific evidence currently includes a limited number of preclinical studies, most notably Aster yomena callus-derived EVs in allergic asthma, whereas many mechanistic claims are extrapolated from colitis, infection, cancer, vascular, or wound-healing models. In parallel, environmental vesicles can promote disease rather than resolve it. Pollen-derived vesicles (pollensomes) and allergen-bearing EVs in indoor dust can protect and co-deliver allergenic proteins, lipid mediators, oxidases, and adjuvant-like signals, thereby facilitating epithelial exposure and type 2 immune activation. This review critically integrates these opposing vesicle contexts. We summarize PDEV biogenesis, isolation, composition, characterization, engineering, loading, and biodistribution; distinguish direct allergic-disease evidence from indirect mechanistic support; and place vesicle actions within the epithelial alarmin-ILC2-Th2-IgE axis and regulatory T-cell, regulatory B-cell, and IgG4-associated tolerance. We further define critical quality attributes, allergenicity testing, release criteria, regulatory considerations, and patient-stratification requirements. PDEVs may offer useful opportunities for allergy nanomedicine, but their translation will require source-specific characterization, rigorous potency and safety assays, and avoidance of unqualified extrapolation from non-allergic models.

Effective therapeutic intervention for central nervous system (CNS) diseases, including brain tumors and neurodegenerative disorders, is significantly challenged by the formidable blood-brain barrier (BBB). This biological barrier severely restricts the passage of most drug candidates, resulting in inefficient delivery to pathological sites and substantially contributing to high clinical trial failure rates for CNS therapies. Engineered nanoparticles have emerged as promising functional material systems capable of navigating these delivery obstacles, offering advantages like encapsulating diverse agents, controlled release, and targeted delivery. This review comprehensively analyzes innovative nanoparticle strategies specifically designed to overcome the BBB and achieve precise CNS delivery via systemic administration. We highlight the critical multi-step biological cascade required for successful therapeutic outcomes: maintaining colloidal stability in circulation, efficiently penetrating the BBB, achieving specific accumulation at the disease site, and effectively engaging target cells. Despite significant advancements, clinical translation of these nanoparticle systems remains limited. A thorough understanding of this multi-step process is paramount to accelerating the clinical application of brain-targeted nanomedicines.