Human sensitization to Prosopis juliflora antigen in Saudi Arabia

Allergenicity to Prosopis juliflora pollen antigen has been reported from only a few countries, including the US, South Africa, India and Kuwait. In some parts of Saudi Arabia, species of Prosopis have been introduced by the millions as roadside ornamentation. There appear to be four flowering seasons during which pollen grains float in all directions. However, the role of Prosopis pollen as the sensitizing and/or triggering agent of allergic asthma and/or rhinitis in the Kingdom has never been evaluated.

A total of 473 allergic patients suffering from bronchial asthma in four different geographical regions (Abha, Qassim, Hofuf and Gizan), and attending allergy clinics and chest disease centers of university and Ministry of Health hospitals in the region were tested for immediate hypersensitivity reaction to Prosopis juliflora allergens. Airborne pollen grains at one center were also studied for one full year, using volumetric sampling techniques.

A total of 76.1% patients in Qassim, 37.5% in Gizan, 29% in Abha and 11% in Hofuf reacted positively to Prosopis antigen. Multiple sensitivities to other pollen antigens were detected in all patients. The level of airborne Prosopis pollen detected in Gizan exceeded 90 grains m -3 of air.

In view of the documented evidence of Prosopis-involved allergenicity, the role of Prosopis pollen as a sensitizing factor in Saudi Arabia has been confirmed. However, the cause of elicitation of symptoms in many multiple sensitive patients, together with the question of cross-reactivities, needs thorough and detailed investigation. In vitro confirmation of all positive results is also required to incriminate Prosopis as one of the major allergens in parts of Saudi Arabia.