What are the advantages and disadvantages of using 5% versus 10% formalin?
Although 5% formalin is thought to provide a more “gentle” fixation of protozoa, this concentration formalin will not always kill all helminth eggs. The 10% formalin will kill most helminth eggs (exception: Ascaris lumbricoides), but may be more damaging to protozoa. In reality, most people probably can’t tell the difference by examining clinical specimens preserved in either 5% or 10% formalin. for environmental reasons, some laboratories have elected to use only the 5% concentration.
