What are allergies?

Allergies and the immune system

One in every two Japanese people suffers from symptoms of some form of allergy.
People have an immune system in order to protect their bodies. If a foreign substance enters the body, the role of the immune system is to target, attack and protect against that substance. It is extremely effective when it works solely against viruses and other such threats to our health. However When the immune system works against essentially harmless substances such as pollen or dust however, it produces symptoms that we refer to as allergies. Substances that cause allergic reactions are known as allergens.
Symptoms caused by allergens include hay fever, allergic rhinitis, atopic dermatitis and food allergies. With the number of allergy sufferers on the increase in recent years, it is thought that one in every two Japanese people now suffers from symptoms of some form of allergy.(*)The increase in allergy sufferers is thought to be down to an increase in allergens that cause allergies, including pollen and dust, and changes in people’s diets and the environment.

(*) Report from the Rheumatism and Allergy Countermeasures Committee (August 2011) Rheumatism and Allergy Countermeasures Committee, Working Group on Disease Control, Health Science Council, Ministry of Health, Labor and Welfare Japan.

Prevalence of allergic rhinitis (seasonal and perennial)
Prevalence of hay feverNumber of atopic dermatitis sufferers

Allergy mechanisms

Imbalances in the immune system, between Th1 and Th2 cells, are linked related to the onset of allergies.
Immune functions protect your body from foreign substances based on a well-balanced mechanism of three immune cells, namely Th1, Th2 and Treg cells. Under normal circumstances (when you are in good health), your immune cells maintain a balance (immune balance). It is when your immune balance becomes imbalanced that you suffer from allergies.
Allergies occur when your immune functions work too effectively against an essentially harmless substance entering your body. When a foreign substance (allergen) enters your body through your nose or mouth, it is detected by dendritic cells on your mucous membrane. Rather than maintaining your immune balance, your body prioritizes Th2 cells, which then work too hard to remove the allergen. This actives B cells and produces an excessive amount of IgE antibodies, which then become attached to the surface of mast cells in preparation for the next allergen entering the body. If the allergen enters the body again, the IgE antibodies on the surface of the mast cells detect the allergen and release excessive amounts of inflammatory factors such as histamines and leukotriene from the mast cells. This brings on allergy symptoms such as sneezing, running nose or congestion.
If you have an immune imbalance, it prompts an excessive defensive reaction from your body, causing the onset of an allergy.