Used in histology to detect and visualize acidic mucopolysaccharides and glycosaminoglycans in tissue sections. Alcian Blue stains these acidic carbohydrates in shades of blue, while the Periodic Acid-Schiff (PAS) reaction highlights neutral mucins and glycogen in magenta or purple. Together, this dual staining technique allows differentiation between acidic and neutral mucins, making it valuable in studying mucin-producing cells in tissues such as gastrointestinal epithelium, respiratory tract, and salivary glands. It is commonly applied in diagnosing tumors, evaluating glandular tissues, and assessing changes in mucin expression in disease states like Barrett’s esophagus or colorectal cancer.