Alcian Blue 8GX is a water-soluble, cationic phthalocyanine dye. It is a mixture of tetramethyl and trimethyl derivatives of copper phthalocyanine, characterized by its bright blue color and positive charge. Its primary and most significant application is in histology and pathology as a specialized biological stain. Alcian Blue 8GX is a classic and essential dye for the selective detection and visualization of acidic mucins, mucopolysaccharides (glycosaminoglycans like hyaluronic acid and chondroitin sulfate), and other acidic carbohydrates in tissue sections. It binds to polyanionic sites via electrostatic interactions. Staining protocols often combine it with Periodic acid–Schiff (PAS) stain (Alcian Blue-PAS or AB-PAS) to differentiate between neutral and acidic mucins, which is crucial for diagnosing various conditions in gastrointestinal, respiratory, and connective tissues. Beyond life science research, it finds use as a colorant in inks and for dyeing textiles, leather, and paper, leveraging its intense blue hue. As a fine chemical powder, standard laboratory safety precautions for handling dyes should be observed.