One of the big problems with scabies is that the mites themselves are too small to see without magnification. Therefore, the rash that develops is often misdiagnosed. Scabies is spread by personal contact, such as by shaking hands or sleeping together or by close contact with infected articles such as clothing, bedding or towels. Scabies can be spread by the insect itself or by the egg.

Apparantly you cant even tell you have scabies for up to three weeks once their fecal starts irritating the skin. The scabies mite is so small that you do not feel them moving around. Though later in the infection you can feel them flutter as they dig into your skin or move.

This does make sense, it seems on my shoulders my skin was thicker and thus I kep getting reinfected there, so just treat more on these areas maybe and the scabies will go away.