Abstract
Background. Lebanon lies within one of the world's most aerobiologically active corridors. Its flora is dominated by a few high-yield anemophilous taxa — Cupressaceae, Olea europaea, Poaceae, Parietaria judaica, and invasive Asteraceae — whose pollen seasons overlap across most of the calendar year. Despite a heavy clinical burden, the Lebanese aerobiological and molecular evidence base is fragmentary and largely over a decade old.
Objective. To consolidate the evidence on the epidemiology, aerobiology, and sensitisation patterns of pollen-induced respiratory allergy in Lebanon, interpreted within the Eastern Mediterranean context, and to translate it into practical clinical implications for the region. This review is deliberately restricted to pollen aeroallergens; cross-reactivity, immunotherapy formulation, and indoor allergens are addressed in companion publications.
Methods. A structured narrative review of PubMed, Scopus, the WHO/IUIS allergen nomenclature database, and the World Allergy Organization aeroallergen database was undertaken between January and April 2026, covering publications from 1990 to April 2026. Studies on aeroallergen sensitisation, pollen aerobiology, molecular allergen characterisation, and climate-driven phenology in Lebanon and neighbouring Eastern Mediterranean countries were selected for relevance, methodological quality, and clinical applicability. Thematic synthesis was performed; no quantitative meta-analysis was attempted.
Findings. Allergic rhinitis prevalence in Lebanon ranges from 21% in school children to 45% (ever) in adolescents, and the first national adult survey reported physician-diagnosed asthma at 6.7%, with allergic rhinitis its strongest predictor. In the largest Lebanese skin-prick series (n = 2,558), any-positive testing reached 75.6%, dominated by house dust mite, Parietaria, grasses, Oleaceae, and Cupressaceae; the national paediatric cohort (n = 919) reported 81.8%, with strong altitude-dependence of mite sensitisation. Beirut aerobiology shows a bimodal calendar with a spring tree-pollen peak (Cupressaceae and Olea) and an autumn weed peak. Substituting older Cupressus sempervirens-based extracts with Cupressus arizonica-based extracts improves detection of Cupressaceae-sensitised patients. Comparators from Turkey, Greece, Cyprus, and Jordan confirm a shared Mediterranean profile. Whole-extract IgE assays are commonly inflated by anti-cross-reactive carbohydrate determinant (anti-CCD) IgE, making a CCD marker essential.
Conclusions. Pollen allergy in Lebanon is shaped by a Mediterranean flora dominated by Cupressaceae, Olea europaea, Poaceae, and Parietaria judaica, with year-round pollen and a bimodal symptom season. The clinical workload is substantial but rests on aerobiological data over fifteen years old and, in most governorates, absent. Coordinated investment in aerobiological monitoring, modernised diagnostic panels (C. arizonica extracts and mandatory CCD markers), molecular profiling, and ragweed surveillance would yield disproportionate clinical and public-health returns within a decade.