No link between allergies and deadly diseases

New research shows that there is no link between allergies and the risk of cancer, severe heart disease, autoimmune diseases, or premature death.

"I think we can breathe a sigh of relief when it comes to allergies. One in five of us have hay fever, so it's a great relief that you don’t need to be particularly concerned about these other diseases, especially cancer," says Professor Hans Jürgen Hoffmann, who studies hay fever at the Institute of Clinical Medicine, Aarhus University, Denmark. He was not involved in the new study.

The research is published in the scientific journal Annals of Oncology.

Allergies do not change the risk of illness or premature death

In the new study, scientists have reviewed the results of five previously published studies to investigate if hay fever sufferers have an increased risk of cancer, autoimmune diseases, type-2 diabetes, or ischemic heart disease--a narrowing of arteries in the heart.

They also looked at the risk of premature death due to conditions such as stroke and cancer. The researchers studied 14,849 people over an 11-year period, and produced four scientific papers that all come to the same conclusion: Having an allergy does not increase your risk of contracting any of these diseases or an early death.

An overactive immune system causes allergies and autoimmune diseases

Many scientists suspected that autoimmune diseases--such as multiple sclerosis and rheumatoid arthritis, wherein the immune system breaks down the body's own cells--were associated with allergies, because incidences of the two seemed to coincide.

But this could be expected if the immune system were to overreact to an allergy, says co-author Clinical Professor Allan Linneberg, from the University of Copenhagen, Denmark.

The immune system can mistakenly try to fight off harmless substances like allergens and, in the case of autoimmune disease, the body’s own cells.

Hay fever sufferers experience this when their immune system mistakenly identifies pollen as a parasite. It triggers a chain reaction to fight this non-existent enemy, which leads to the familiar symptoms of red eyes and a runny nose.

People with autoimmune diseases also fall victim to such an overactive immune system, and their own cells become the target.

Cancer tricking the immune system

Such a case of mistaken identity could help explain why cancer spreads and begins to grow unchecked.

Normally, the immune system’s T-cells detect damaged or mutated cells in the body and destroy them. But cancer, rather cleverly, is able to attract other immune cells that inhibit T-cell formation.

The cancer is effectively surrounded by an army of the body's own immune cells that protect the tumour, enabling it to grow.

Therefore, some scientists postulated that whilst allergies kept the body busy fighting off these harmless allergens, cancer could develop unchecked.

The new study suggests, however, that is not the case.

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Read the Danish version of this article on Videnskab.dk
 

Translated by: Catherine Jex

Scientific links

• Specific IgE positivity against inhalant allergens and development of autoimmune disease, Autoimmunity 2015, DOI: 10.3109/08916934.2014.1003640
• Atopy and cause-specific mortality, Clinical & Experimental Allergy 2014, DOI: 10.1111/cea.12408
• The association of atopy with incidence of ischemic heart disease, stroke, and diabetes, Endocrine 2015, DOI: 10.1007/s12020-014-0321-z
• Atopy and Development of Cancer: A Population-Based Prospective Study, The Journal of Allergy and Clinical Immunology in Practice 2014, DOI: http://dx.doi.org/10.1016/j.jaip.2014.06.010

External links

• Allan Linneberg
• Hans Jürgen Hoffmann

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