Allergies and Autoimmunity

Allergies and autoimmune diseases are both conditions that result from an inappropriate immune response.

“In the case of autoimmunity, it is an inappropriate response to a self-antigen, while in the case of allergy it is an inappropriate response to a harmless environmental antigen, such as grass pollen or cat dander,”

said Steven F. Ziegler, the director of the Immunology Program at the Benaroya Research Institute at the University of Washington.

One similarity in the pathways of development between allergies and autoimmune diseases is the involvement of immune cells in the immune response. (1) With allergies, the immune system reacts to harmless substances or allergens, which leads to the activation of immune cells. (2) Similarly, in autoimmune diseases, immune cells may recognize self-tissues as foreign and mount an immune response, resulting in tissue damage and inflammation. You can read more about the specific body regions commonly affected by autoimmunity in our other article.

Environmental factors such as allergens, medications, and toxins can trigger or exacerbate allergic reactions, while infections, stress, and exposure to certain environmental toxins have been implicated in triggering or exacerbating autoimmune diseases. (3)

Genetic factors also play a role in the development of both allergies and autoimmune diseases. Certain genes are associated with an increased risk of developing allergies or autoimmune diseases, and genetic factors can influence immune cell function, cytokine production, and other immune responses.

“As we learn more about the immune responses in autoimmunity and allergy, we are discovering that in some cases variants of the same gene are involved in both. This suggests a connection between these immune-mediated diseases,”

said Ziegler. “As is often the case in immunology, the more we learn about one type of immune-mediated disease, the more we find commonalities with others.”

While allergies and autoimmune diseases share some similarities, including the involvement of immune cells and genetic factors, they diverge at certain points. One key area of interest between autoimmune diseases and allergies is the type of immune cells involved. (4)

According to Ziegler, there is an overlap between the cell types involved in autoimmunity and allergy in that both have pathogenic CD4 T-cells (self-reactive in the former, allergen-reactive in the latter) as well as B cells.  Additional cell types are unique to each disease, such as (e.g., mast cells in allergy).  Immune cells can drive inflammation and tissue damage in the target organs.

Some studies have shown that individuals with allergies may have an increased risk of developing autoimmune disease and vice versa. This suggests that there may be some shared genetic or environmental factors that contribute to the development of both conditions.

For example, a study published in the journal International Review of Rheumatic Diseases found that patients with systemic lupus erythematosus (SLE), an autoimmune disease, had a higher prevalence of allergic rhinitis compared to healthy controls. Another study published in Allergy, Asthma and Clinical Immunology found that patients with rheumatoid arthritis, also an autoimmune disease, had a higher prevalence of atopic dermatitis, a type of skin allergy.

That being said, the relation is not direct. 

“The frequency of allergy in the general population is quite high (about 20% of Americans), while the frequency of autoimmune disease is (between 5 and 7%),” said Ziegler. “Thus, the likelihood that some individuals with allergies will also develop autoimmune disease is relatively high.”

While there are anecdotal reports of responses to some allergens also causing autoimmunity, such an effect of allergic responses is not generally seen, according to Ziegler. 

Overall, the relationship between allergies and autoimmunity is complex and often varies depending on the individual, the specific allergen or autoimmune disease, and other factors. Not all individuals with allergies will develop autoimmune diseases, and not all autoimmune diseases are triggered or exacerbated by allergies. 

Understanding the association between allergies and autoimmune diseases could have important implications for diagnosing, managing, and treating immune-mediated disorders. It is important to find specialists who can collaborate on care when possible in order to fine-tune a treatment plan.