Manufacturers use various combinations of the leaves, stems, roots, and other plant parts. A botanical's active components may concentrate in a specific location within the plant. Dosage formulations are also left to the manufacturer's discretion. The content and potency of botanical products may vary greatly depending upon the formulation. It is difficult to control the amount of dietary supplement delivered by a tea preparation because brewing times are likely to be dissimilar.
Contamination is an issue for botanical agents.
Products that are collected from wild sources have the potential of being tainted by radioactivity or heavy metals. Both wild and cultivated botanicals may have pesticide residues. Additionally, microbial and parasitic infestation may be present. Development of standards for botanicals is fundamentally complex, as evidenced by the aforementioned reasons. There are also difficulties in designating assay methods that are feasible for the producers of botanical products to conduct without prohibitive cost.