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An autoimmune disease is when your body attacks itself, and it’s possible giving yourself a parasite gives it something else to focus on…

It's more complex than that. If someone is exposed to parasites when they're still developing, their chances of having autoimmune issues later in life goes down – the fancy way to say that is that exposure to some parasites lessens the chances of immune system dysregulation. Some parasite proteins can also be used to modulate the immune system to eg. treat asthma. See eg. Helminth Immunomodulation in Autoimmune Disease from 2017, abstract here:

Helminths have evolved to become experts at subverting immune surveillance. Through potent and persistent immune tempering, helminths can remain undetected in human tissues for decades. Redirecting the immunomodulating “talents” of helminths to treat inflammatory human diseases is receiving intensive interest. Here, we review therapies using live parasitic worms, worm secretions, and worm-derived synthetic molecules to treat autoimmune disease. We review helminth therapy in both mouse models and clinical trials and discuss what is known on mechanisms of action. We also highlight current progress in characterizing promising new immunomodulatory molecules found in excretory/secretory products of helminths and their potential use as immunotherapies for acute and chronic inflammatory diseases.

But man, that sounds like when people gave themselves tapeworms to lose weight. There was some vague logic to make it sound ok. But any medical professional that condoned it probably wasn’t a very good doctor.

Especially if they are infecting people to treat autoimmune disorders

Just because giving someone a tapeworm for weight loss is not a great idea doesn't really mean anything here. Immunomodulatory therapy with parasites isn't woo-woo despite how weird it may sound, and the idea isn't to necessarily give people worms (although that's not entirely ruled out either!) but to learn how they do what they do