What causes tree nut allergies?

    Written by:
    Rachel Hathcock

    Fact-checked

    by:

    Bill Willis, James Gaylor
    Last Updated: May 16, 2025

    Tree nut allergies occur when the immune system mistakenly identifies proteins in tree nuts as harmful invaders, which leads to an inappropriate immune response. This reaction involves T helper 2 cells and the production of IgE antibodies, which result in allergic symptoms, although the reasons for this abnormal immune response are not fully understood.

    Tree nut allergies are caused by an inappropriate reaction of the immune system to the proteins found in tree nuts. Normally, the immune system targets and attacks pathogens like viruses and bacteria but in the case of food allergies, the immune system identifies a certain food as an “invader” and launches an immune response against it.

    This breakdown of immune tolerance is primarily driven by T helper 2 cells and often includes the production of food-specific IgE antibodies, all of which lead to a cascade of immune responses (like the activation of mast cells and release of cytokines) that cause allergic symptoms. Why the immune system reacts abnormally to certain foods in some people is not fully understood.[1]