Background: The seeds of Plantago ovata (psyllium, ispaghula) used in the manufacture of bulk laxatives are known to be the cause of occupational allergy (rhinitis, asthma) in health care and pharmaceutical workers.

Objective: We studied the prevalence of P ovata seed allergy among health care workers in geriatric care homes and compared it with a group of health care professionals not exposed to P ovata seed. Cross reactivity with Plantago lanceolata pollen was also studied.

Methods: Two groups of health professionals were recruited: 58 health care workers from geriatric care homes who were exposed daily to laxatives containing P ovata and 63 nonexposed health care professionals. The prevalence of allergy and sensitization to P ovata seed was determined based on clinical history, skin prick test, and analysis of specific immunoglobulin (Ig) E. IgE immunoblotting was performed to calculate the molecular weights of the P ovata seed allergens. Cross reactivity to P lanceolata pollen was studied by enzyme allergosorbent test (EAST) and immunoblot inhibition techniques.

Results: The prevalence of sensitization and clinical allergy to P ovata seed in the exposed group was 13.8% and 8.6%, respectively. No sensitization was observed in the nonexposed group. IgE-binding proteins of 17, 20, 25, 32-34, 54, 73-77, and >97 kDa were identified. EAST inhibition and immunoblot inhibition demonstrated the existence of cross reactivity between P ovata seed and P lanceolata pollen extracts.

Conclusions: The rate of sensitization to P ovata seed is high among health care workers in geriatric care homes (13.8%). A mild cross reactivity between P ovata seed and P lanceolata pollen was observed.

Key words: Plantago ovata. Plantago lanceolata. Occupational allergy. Prevalence. Health care workers. Cross reactivity.