People who take bee pollen supplements need to know that it can cause potentially life-threatening reactions in those with seasonal allergies, doctors warn.

Bee pollen is a natural health product made from pollen granules collected by bees. It's touted to aid in weight loss and promotes longevity.

People with pollen allergies may have allergic reactions, including anaphylaxis, from ingesting bee pollen. (iStock)

In Tuesday's issue of the Canadian Medical Association Journal, doctors describe how they treated a 30-year-old woman who was referred to an allergy clinic after having an anaphylactic reaction from bee pollen supplements.

"Anaphylaxis associated with the consumption of bee pollen has been reported in the literature, but many people remain unaware of this potential hazard," wrote Dr. Amanda Jagdis of the University of British Columbia and Dr. Gordon Sussman of St. Michael's Hospital and the University of Toronto.

"Patients with pollen allergies should be advised of the potential risk when consuming these products because it is not known who will have an allergic reaction when ingesting bee pollen."

The problem can arise since bees collect a variety of pollens, including airborne ones that commonly cause allergies, such as ragweed.

In the paper, the woman had seasonal allergies but no history of allergies to food, drugs, insects or latex.

Her eyelids, lips and throat swelled, she had difficulty swallowing, hives and other life-threatening symptoms, the doctors said.

After emergency treatment, she stopped using the bee pollen supplements and had no other reactions.

In 2006, Greek investigators looked at the association between pollen and bee pollen allergy.

Among 145 patients and 57 healthy controls who had skin tests for reactions to bee pollen, 73 per cent of the allergy patients also had positive skin test reactions to at least one bee pollen extract.

The commercial pollen extracts tested included olive, grass and bugwort pollens.

The authors prescribed an auto-injector to the woman given the life-threatening nature of her reaction. They acknowledged that there's controversy over the necessity of the prescription.

Sussman is a consultant for drug maker Pfizer and has received grants from Novartis and CSL Behring.