The signs and symptoms of a parasitic infection may take several weeks, months, or even years to develop. And the symptoms that do develop can often be confused with other illnesses. Constipation, diarrhea, gas, bloating, irritable bowel syndrome, joint and muscle pain, anemia, allergies, skin conditions, nervousness, sleep disorders, teeth grinding, chronic fatigue syndrome, and immune dysfunction are all common symptoms of a parasitic infection.