Thanks for your question.
Trichomonoiasis is an STI that can be passed through unprotected sex. Trichomonoiasis does not normally live on the hands, unless you touch the genitals of someone who has it. If you get sexual fluids on your hands from someone who has Trichomoniasis, then washing your hands is a good idea.
Trichomonoiasis is a parasite that cannot live outside the human body, and would likely die very soon after being on your hands (even without washing), but washing your hands will make it even less likely.
If you are touching the genitals of someone who has Trichomonoiasis, and then plan to touch your own (or someone else’s) genitals right away, then it’s definitely important to wash your hands, as there may not be time for it to die off first.
If you have tested positive for Trichomonoiasis you need to get treatment with medication, washing your hands will not treat an infection inisde your body.
Hope this helps, please feel free to submit another question as needed.