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Tirumalai Kamala:
No, allergy is not a sign of decreased immunity. It is a specific type of immune dysregulation. Autoimmunity, inflammatory disorders such as IBS and IBD, and even cancer, are examples of other types of immune dysregulation.
The quality and target of immune responses, not their strength, is the heart of allergy. Let's see how.
-Allergens – substances known to induce allergies – are common. Some, such as mites and pollen, are even ubiquitous.
– Everyone is exposed to allergens while only a small number of them are clinically diagnosed with allergy.
-Therefore, allergens do not inherently cause allergy. They can, but only in those who are predisposed to allergy, not everyone.
-Everyone allergic causes pathological immune responses not only to one or more structural allergens, while non-allergic ones do not.
– Allergy sufferers are not necessarily more sensitive to other diseases.
If the immune response of each allergic person is selectively deformed when responding to specific allergens, what makes a person allergic? Obviously, a mix of genetic and environmental factors.
[The] thing is that the prevalence of allergies has increased in recent decades, especially in developed countries, [which is] a period too short for purely genetic modifications to be based on genetic mutations, as it would take several generations to have such an effect on the entire population. That makes the difference in favor of environmental change, but what exactly?
From the 1960s, epidemiologists began to report a link between infections and allergies …[the] more infections in childhood, [the] less the risk of allergy [this is called hygiene hypothesis]. At the time, the microbiota was not even a consideration, but now that we have learned better, the hygiene hypothesis has expanded to include them.
The idea is essentially that the current Western lifestyle, which developed rapidly during the twentieth century, has reduced all their lives and, above all, their early exposure to environmental microorganisms, many of which would normally have been part of the gut microbiota of an individual after birth.
How could changes in the composition of the gut microbiota lead to selective allergies in specific individuals? Genetic predisposition should be considered as a given. However, natural history suggests that such predispositions have become much rarer than ever in a full clinical state.
Let's see briefly how this equation could have fundamentally changed in recent times. Consider indoor sanitation, chlorinated water, caesareans, formula, ultra-processed foods, lack of regular contact with farm animals (substitutes for nature), and misuse, ubiquitous, even excessive antimicrobials such as antibiotics, just quote a few important factors.
Although some of them have been beneficial in their own way, epidemiological data now suggest that such innovations in living conditions have also disrupted the intimate association with the natural world that had been the norm for human societies for some time. immemorial. In the process, such dramatic changes seem to have profoundly reduced the diversity of the human intestinal microbiota in many, mainly in developed countries.
Without our knowledge, a epidemic of absence* As Moises Velasquez-Manoff so aptly puts it, it is thus manifested invisibly in many human societies during the twentieth century, along with the evolution of the standard of living.
Such a sudden and profound reduction in gut microbiota diversity then appears as the trigger that transforms the normally hidden predisposition in some into a clinically manifest allergy. The actual mechanisms of the process remain the object of active research.
We (my colleague and I) propose a new predictive mechanism explaining how the disruption of regulatory T cell function ** constitutes the decisive and non-negotiable link between the loss of a specific microbiota and inflammatory disorders such as the allergies. Time (and data to support) will tell if we are right.
* An absence epidemic: a new way to understand allergies and autoimmune diseasesMoises Velasquez-Manoff
** a small indispensable subset of CD4 + T cells.
This post originally appeared on Quora. Click here to see.
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