Azure B is a blue basic dye and is one of the components in the thiazine dye group. It has a range of applications in both histology and cytology. Specifically, Azure B is often used in combination with other dyes in various staining protocols.

1. Romanowsky stains: Like Azure A, Azure B is also utilized in the preparation of Romanowsky stains when combined with eosin and other dyes. Romanowsky stains, such as Wright's stain, Giemsa stain, and Leishman's stain, are used for blood smears to differentiate and classify blood cells, as well as to identify blood parasites like Plasmodium spp., the causative agent of malaria.

2. Mast cell staining: Azure B can be used to stain mast cell granules, emphasizing them for easy identification.

3. Methylene blue-azure II stains: In cytology, a combination of methylene blue and Azure II (which contains Azure B) is used for staining exfoliative cells, aiding in the identification of cellular abnormalities.

4. Toluidine blue stain: Azure B might also be present in some formulations of toluidine blue stain, which is used for various purposes, including staining acidic polysaccharides, mast cells, and highlighting metachromatic areas in tissue sections.

Azure B, in combination with other dyes, plays an essential role in helping researchers and clinicians differentiate various cell types and structures, thereby aiding in diagnosis and research.