Sensitization and Allergies of Herbal Products

Abstract

The most common example for an allergy to herbal material is rhinoconjunctivitis, better known as “hay fever.” It is estimated that between 10 and 40 % of the world’s population suffers from allergic rhinoconjunctivitis (Bachert et al., Allergy 65 (Suppl 93): 1–13, 2010). But food allergies, which are estimated to affect 1–10 % of the world’s population, including allergies to plant-derived materials such as wheat, soy, peanuts and tree nuts, are also prevalent (Quake and Nadeau, Semin Cell Dev Biol, 43: 125–130, 2015). While most of the cases will also refer to animal proteins (milk, egg, fish), separate numbers for plant food allergy are not available. Also, medicinal products containing herbal substances/preparations may provoke allergies. Not only can the processed forms trigger allergies, the starting material (plants) may provoke allergic reactions as well, either in individuals involved in harvesting or processing, or in persons concocting preparations (Sticher et al., Hänsel/Sticher – Pharmakognosier Phytopharmazie. Wissenschaftliche Verlagsgesellschaft mbH, Stuttgart, 2015), such as pharmacists or nurses; this has in particular been reported for Psyllium.

Beside these facts, it should not be forgotten that a “food/plant allergy” is inferred by patients or consumers, whereas signs of allergy have effectively been triggered by food additives (i.e., artificial coloring), excipients, fungal spores, or contaminants. Therefore, in most cases, it is not, or at least hardly ever, possible to pinpoint the triggering agent and to confirm or exclude herbal preparations as allergic agents. This chapter will focus mainly on herbal preparations found in food supplements or medicinal products; however, there are flowing transitions to food, cosmetics, and environmental herbal products such as pollen.