Hello - parasites can live in EVERY part of the body including the eyes, brain, sinus cavities and the blood. Muscles and organs host parasites, larvae and eggs too. 70% of parasites are microscopic (one cell protozoa) and can live in any single cell. That's why HUMAWORM is so effective - it is formulated to remove ALL parasites from ALL parts of the body, including the blood. I hope this helps!