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Recent studies suggest allergies start from the skin?

Kanami Orihara
Assistant Professor, Waseda Institute for Advanced Study, Waseda University

I am engaged in allergy research.

Allergic diseases are one of the most common conditions found in people of all age groups. Allergy is an immunological reaction against proteins commonly found in food, house dust mites, or pollens. It causes symptoms in the respiratory system including the nose and bronchi, the dermatological system, and the digestive system. It may even cause severe systemic symptoms. Many researchers have studied allergies and developed treatments for each of those specific symptoms. Today, many symptoms can be alleviated by many different types of drug even including biological drugs and immunotherapy, and combinations of those drugs and therapies.

What are allergies?

Allergy is an overreaction of the immune system. The immune system protects our body from external bacteria and viruses. Skin, hair, sweat, tears, saliva, and gastric acid are all immunological barrier systems. If foreign substances pass these primary physical and chemical barriers, the immune cells come into play. The immune system treats foreign substances as “non-selves” or as enemies, and allergy occurs when the immune system excessively reacts to these invaders. Food allergies occur when the immune system identifies proteins in eggs, wheat, or milk as foreign substances. Similarly, mite feces or cedar pollens can cause bronchial asthma, pollen allergies, or atopic dermatitis.

Do allergies start from the skin?

Recent hot topic in allergy research is skin sensitization, or the study of mechanisms that cause allergies to start from the skin.

Skin is the immune system’s first barrier of defense. Recent studies showed a weakened skin barrier can lead to allergies.

The immune system produces IgE to defend itself when the barrier is weak and foreign substances enter through the skin. This causes the host of the immune system to develop allergies to the foreign substance. Recent studies demonstrate that the same process applies to bronchial asthma and food allergies.

An increased food allergy risks caused by epidermal sensitization to food antigens was proposed as the dual-allergen exposure hypothesis (J Allergy Clin Immunol. 2008 Jun; 121(6): 1331-6) and quickly received attention. Many substances, or allergens, can cause food allergies. They are too small to see, but can be found on tables, floors, and in the air. Individuals with cracks in their skin barrier caused by rashes or dry skin, especially in babies, whose skin immune functions have not fully developed, can become allergic to these substances. For defensive purposes, our immune system memorizes those allergens, and prepare for foreign substances’ next "attack". When allergens do enter the next time, allergic reactions occur; food intake can result in digestive symptoms, and inhalation of pollens through the nose can cause sneezing and/or a runny nose.

Up to about a decade ago, some people believed that food allergies develop in babies because their digestive tract system is not matured enough so that it can lead misrecognition of foreign substances. This sometimes led to diet control for pregnant and/or breast-feeding women as well as limited ingredients in baby food. However, recent studies claimed that such dietary restrictions in fact increase food allergies risk factor (N Engl J Med. 2015 Feb 26; 372(9): 803-13). More specifically, dietary restrictions prohibit development of immune tolerance, which can be obtained through oral allergen intake and which suppress allergies that leads the immune system to learn those antigens. Of course, we still cannot rule out the possibility of sensitization for food allergies occurring via the digestive tract. However, skin sensitization continues attracting the attention of many researchers and there is still no evidence that avoiding particular kinds of food can prevents developing food allergies.

Preventing allergies

Once individuals become allergic, they develop allergic reactions every time they are exposed to the allergen due to the memory function of the immune system. To counter this mechanism, research has been carried out on clinical condition mechanisms and preventing allergies. Recently, there was a notable finding by a group from the National Center for Child Health and Development, my partner research organization. In their research, newborn babies with high risks in atopic dermatitis were studied. The study indicated that the group in which a moisturizer was applied to the entire body every day developed atopic dermatitis in more than 30% less frequency, compared to another group in which Vaseline was applied only to dry skin areas as necessary (J Allergy Clin Immunol. 2014 Oct; 134(4): 824-830.e6.). This means that maintenance of healthy skin and prevention of epidermal sensitization suppressed development of atopic dermatitis. Other allergy studies include research on the balance of intestinal bacteria, but they have not reached a definitive conclusion. In addition to further research on clinical condition mechanisms, I believe that the field of preventative medicine will continue to expand in the future.

Kanami Orihara
Assistant Professor, Waseda Institute for Advanced Study, Waseda University

Kanami Orihara has been an Assistant Professor at Waseda Institute for Advanced Study, Waseda University since 2014. Her prior career includes a Post-Doctoral Research Fellow at the National Research Institute for Child Health and Development, and a Post-Doctoral Fellowship at the Department of Immunology, School of Medicine, University of Manitoba (Canada). She received her Ph.D. in Pharmaceutical Sciences, Showa University (Department of Allergy and Immunology, National Research Institute for Child Health and Development). Before receiving her M.Sc. in Bioscience and Biotechnology, Tokyo Institute of Technology, she graduated with a B.Sc. (Pharm) in Pharmaceutical Sciences, Tokyo University of Science.