Old Friends Theory

An explanation for the Autoimmune Disease Epidemic

Autoimmune diseases arise from abnormal immune response against substances and tissues normally present in the body.


There are over 100 known autoimmune diseases affecting one in five Americans.

In recent decades, prevalence of these diseases have increased at an alarming rate.

  • Allergies
  • Celiac Disease
  • Crohn’s Disease
  • Lupus
  • Multiple Sclerosis
  • Psoriasis
  • Type 1 Diabetes

The “Old Friends Theory” suggests that humans evolved with a range of microbes, creating a relationship of interdependency and symbiosis.

Over millennia, humans were under unremitting selection pressure as they came into constant contact with microbes and pathogens. For perspective, modern humans dispersed from Africa roughly two hundred thousand years ago whereas bacteria pre-date human existence by millions of years. While parasites are traditionally thought to be “bad”, recent discoveries reveal greater importance of micro-organisms in the ecology of the human body. Certain co-evolved parasites, or “old friends”, are not harmful, but possibly crucial to healthy human existence.

Intestinal microbes and helminths evolved to regulate the human immune system.

While the body typically declares war on foreign invaders, helminths have been demonstrated to down-regulate the immune system to keep themselves from being wiped out. The dampening effect on the immune system creates higher response threshold for all foreign bodies including pollen, foods, and other antigens. Helminths naturally reduce inflammation and promote diversity of gut flora – two factors that are a common thread across nearly all autoimmune disorders.

Industrialized countries have higher rates of autoimmune disorders than those of undeveloped countries.

Modern flush toilets, sewage systems, and germ-free living have broken the natural lifecycle with our old friends. Other parts of the world, typically poor rural areas, suffer far less from immune disorders.

Growing up without “old friends” may create an unbalanced immune system leading to autoimmune disorders.

The development of a child’s immune system is at its most pliable in the earliest years, months, and even seconds of a child’s life. First contact with bacteria and pathogens create long-lasting impressions for immunity; and maternal infection plays an important role in development of the fetus.


Academic research accelerates in support of the Old Friends Theory.


Helminthic therapy, the treatment of auto-immune disorders using various helminths, is being developed and tested.