I definitely don't like:
forma especializada de su cuerpo. I don't think it is the right translation.
Especializar in Spanish has a different meaning and here we are talking about a
special shape in a body, not a
specialized shape.
So I would just say that: La forma especial del cuerpo del piojo y su pequeña cabeza ovalada, le permiten moverse libremente entre los pelos de la cabeza (o los cabellos) de la persona.
I think this way you don't need to say if it's tu/su cabeza and avoid any confusion. If you translate cabellos don't have to say pelos de la cabeza. right?
I hope it helps!!! yeah, I am scratching already!!!
