Which stain is used to stain collagen red?

• A. Van Gieson
• B. Masson trichrome
• C. Oil Red O
• D. Mast cells

Answer: (A)

Van Gieson staining uses a combination of picric acid and acid fuchsin so collagen fibers appear red or pink, while surrounding muscle and cytoplasm take on a yellow hue and nuclei stain dark. This color contrast makes it easy to identify and quantify collagen in tissues, which is especially helpful when assessing fibrosis or connective tissue quality. Masson trichrome, by contrast, usually colors collagen blue or green, not red, so it wouldn’t produce the red stain you’re looking for. Oil Red O targets lipids in frozen sections, not collagen, and staining mast cells refers to highlighting a cell type rather than a tissue component with a specific color.