Here's a simple test that you or your doctor can do when you're asking the "is it scabies" question. First, look carefully for fresh itchy bumps or thin grayish squiggly lines (burrows) in the skin, especially at hands, inner wrists, fingerwebs, elbows, armpits, ankles, feet, diaper area, belt-line, and abdomen. Infants and young children can get scabies on the face, scalp, and neck, unlike older folks. Magnifying glass and bright light can help.
Take a dark washable wide-tip marker, and rub around the suspicious bumps or burrows. Then take an alcohol wipe or alcohol-soaked gauze and wipe away the ink. If there's a scabies burrow under the skin, the ink often remains, showing you a dark irregular line. Occasionally a tiny dark dot is visible at the end of the burrow - that's the mite.
At the doctor's office, we might use mineral oil and a scalpel to scrape the burrow and a fresh bump or two onto a microscope slide, to look for the mite, or its eggs and feces. But the ink test can be done at home, if you're curious that way. In children recently adopted from institutional care, we do have a pretty low theshold to treat for scabies for intensely itchy skin rashes.