Demodex, a microscopic parasite which causes skin and outer ear problems in some prople looks sort of like a rotifer. A different species causes mange in pets. A guy on the parasite Support forum posted about a similar problem, had some small parasite looking things in his cracked heels. I suggested he take zinc to stop his heels from cracking and use a balanced Vit B supplement for skin health. Skin parasites such as mites can be treated with Diatomaceous Earth and there are several natural treatments online which contain various oils. Search for 'human demodex'
There are many parasites which normally infest other animals or are free living which can rarely infest humans. All that they need are a suitable environment. Hulda Clark suggested that one reason they can live in humans is that there is a pollutant present which they require to live or require to cause disease. She would advise serious detoxing and improving immune system health and whole body health.