Why Do Humans Have Allergies?

Allergies are caused by your immune system reacting to specific molecules. The human immune system has several varieties of antibodies (the parts that detect pathogens and cause immune reactions). There are five in fact: IgA, IgD, IgE, IgG, and IgM. IgE is the antibody that is associated with allergies (an overreaction by this antibody).

Interestingly, IgE is only found in mammals, making it ‘young’ (on the evolutionary timeline) compared to those found in fish, reptiles, and insects. Part of the theory behind allergies considers that IgE is ‘new’, its cutting edge, and could be considered a work-in-progress (in evolutionary terms).

Interestingly, IgE also fights intestinal worms, so some experts believe that parasitic worms (Helminths) are necessary for the immune system to properly regulate itself, as we humans evolved alongside them. The parasite reduces the amount of IgE in the body to stop the body from attacking itself. There are ongoing tests, where doctors are trying to treat immune disorders (such as Lupus, Rheumatoid Arthritis, and psoriasis), and common allergies (such as hayfever) with parasites. Results have been fairly hopeful.