Merthiolate Formalin Solution is an important component of the MIF-Color staining kit, which is used to stain and fix stool samples for the detection of parasites. When applied, the solution rapidly penetrates tissue samples where formaldehyde causes cross-linking with certain amino acids in the proteins present. This process serves to preserve the proteins and cellular organelles and results in fixation of the tissue samples. This fixation is not selective, which can lead to cross-linking of target proteins with unrelated proteins. This can reduce immunoreactivity, but antigen retrieval methods can often reverse undesirable changes caused by fixation. Optimization of fixation protocols in terms of time and temperature is critical, as over- or under-fixation can lead to inaccurate results.