Do parasites have any benefit to humans?

Parasites can offer some benefits to humans. For example, early infections with parasites decreases your risk of allergy or autoimmune disease, probably because the parasites keep your immune system occupied. If you live in an environment that is too sterile, your immune system gets bored and starts attacking harmless objects (like pollen or shrimp) or even your own body. Doctors think this may be one of the big reasons allergies and autoimmune diseases have become so much more common in the modern, more hygienic era.