Background: Herbal formulations represent a significant segment of global healthcare, with over 80% of the world’s population relying on traditional plant-based medicines as a primary or supplementary therapeutic resource.

Objectives: This review systematically examines the types and sources of impurities in herbal formulations, their toxicological consequences, analytical methodologies for their detection, and evidence-based quality control strategies.

Methods: A comprehensive literature search was performed across PubMed, Scopus, Web of Science, and WHO technical reports published between 2000 and 2024, focusing on peer-reviewed studies addressing contamination, standardization, and regulation of herbal products.

Results: Impurities in herbal formulations include microbial contaminants, heavy metals (lead, mercury, arsenic, and cadmium), pesticide residues (organophosphates, organochlorines, and carbamates), mycotoxins, adulterants, residual solvents, and processing by-products. These arise at all production stages—cultivation, harvesting, processing, and storage—and can cause acute toxicity, chronic organ damage, endocrine disruption, carcinogenicity, and reduced therapeutic efficacy. Advanced analytical platforms (GC-MS/MS, LC-MS/MS, ICP-MS, biosensors, DNA barcoding) now offer sensitive multi-residue detection. Adherence to Good Agricultural and Collection Practices (GACP), Good Manufacturing Practices (GMP), and harmonized regulatory frameworks (WHO, USP, Ph. Eur.) is essential.