Difference Between Stain and Dye in Histology

The main difference between stain and dye in histology is that stain is a mixture of several dyes whereas dye is a substance that highlights intracellular or extracellular elements of a tissue. In addition, a stain gives contrast to the tissue as it highlights different components with different colors. On the other hand, a dye may highlight only a specific component within a tissue.

Stain and dye are two types of chemical reagents used in the staining process of the tissues. They give an inherent contrast under the microscope.

Key Areas Covered

1. What is a Stain
     – Definition, Facts, Common Stains
2. What is a Dye
     – Definition, Acidic Dyes, Basic Dyes
3. What are the Similarities Between Stain and Dye in Histology
     – Outline of Common Features
4. What is the Difference Between Stain and Dye in Histology
     – Comparison of Key Differences

Key Terms

Acidic Dye, Basic Dye, Cellular Components, Stain

What is a Stain

A stain is a mixture of dyes that enhance the contrast of the microscopic image. In general, most cells that make up tissues are colorless and transparent. Therefore, tissues are stained in such a way to make the cells visible. The chemical reagents used in the technique are the stains. Each dye within the stain selectively highlights a particular chemical entity within a tissue. Therefore, several components of the tissue can be in different colors. Hence, stains give a contrast to the microscopic slide.

Figure 1: Human Lung Tissue Stained with H&E

Common Stains

What is a Dye

A dye is a single chemical component contained in a stain. A single dye can highlight a specific type of chemical entity within the tissue. Therefore, in order to highlight several components in the same slide, a mixture of dyes has to be used. The two main types of dyes are acidic dyes and basic dyes.

Basic dyes react with anionic/acidic components of the tissue such as nucleic acids.   

Basic Dyes

• Methyl green – Green in color
• Methylene blue –  Blue in color
• Pyronin G –  Red in color
• Toluidine blue –  Blue in color

Figure 2: Human Cheek Cells Stained with Methylene Blue

Acidic dyes react with the cationic/basic components of the tissue such as proteins.

Acidic Dyes

• Acid fuchsin – Red in color
• Aniline Blue – Blue in color
• Eosin – Red in color
• Orange G – Orange in color

Similarities Between Stain and Dye in Histology

• Stain and dye are two types of chemical reagents used to highlight specific components of a tissue.
• Both are used in the histological and histopathological studies.

Difference Between Stain and Dye in Histology

Definition

Stain: A mixture of selected dyes to color a particular biological specimen

Dye: A single chemical reagent contained in a stain

Significance

Stain: A mixture of dyes

Dye: A chemical reagent

Colors

Stain: Highlights different components in different colors

Dye: Only highlights a specific component of the tissue in one color

Role

Stain: To give a contrast to the tissue

Dye: To highlight a specific component within a tissue

Examples

Stain: H&E, toluidine blue, Masson’s trichrome stain, Wright’s stain

Dye: Methyl green, pyronin G, Aniline Blue, orange G

Conclusion

A stain is a mixture of dyes that give a contrast to the different components of a tissue on a microscopic slide while a dye is a chemical reagent that highlights a specific entity in the sample. The main difference between stain and dye is the role of each solution in histology staining.

Reference:

1. “Histology Stains.” PROTEIN SYNTHESIS BASICS, Available Here
2. Paxton, et al. “Histological Stains Other than H&E Acid and Basic Dyes.” Histology Guide, The Leeds Histology Guide, 1 Jan. 1970, Available Here

Image Courtesy:

1. “Emphysema H and E” (CC BY 2.0) via Commons Wikimedia
2. “Human Cheek Cells” By Joseph Elsbernd (CC BY-SA 2.0) via Commons Wikimedia