Why immune conditions are rising.

Allergy and autoimmunity are climbing across the modern world. The emerging science points less to our genes than to the world we have built around ourselves.

In a single lifetime, allergic and autoimmune conditions have moved from uncommon to everywhere. Together they now affect more than a billion people worldwide, having risen to what researchers openly call epidemic proportions.¹ And the numbers are still climbing.

A change too fast for our genes

The speed of the rise is itself a clue. Our genes do not change meaningfully in a few decades, but our environment has changed enormously. One striking marker makes the shift visible: antinuclear antibodies, a common signal of autoimmunity, rose in United States adolescents from 5.0% in the late 1980s to 12.8% by 2011–2012.² In the United States, the number of people diagnosed with an autoimmune disease is estimated to be rising by 3–12% every year.³

The hygiene hypothesis

The leading early explanation is the “hygiene hypothesis.” As infections became less common in industrialised countries, an immune system shaped over millennia to expect constant microbial challenge began, in effect, to misfire, reacting to harmless targets such as pollen, food proteins, or the body's own tissues.⁴ Migration studies are especially telling: people who move from a low-incidence country to a high-incidence one can acquire the higher risk within a single generation.

A natural experiment along the border between Russian Karelia and Finland, genetically similar populations living in very different conditions, found sharply different rates of allergy and autoimmunity, with far more disease on the wealthier, more sanitised Finnish side.⁵

Our genes did not change in a generation. Our world did.

From hygiene to barriers

The idea has since evolved. A newer framing, the “epithelial barrier hypothesis”, proposes that many modern exposures, from processed foods and detergents to pollutants and microplastics, damage the protective barriers of the skin, gut, and airway. When those barriers weaken, the immune system meets substances it was never meant to, and can lose its tolerance for them.¹ It is unlikely to be one cause, but a web of them acting together.

Why it matters for how we respond

If this rise is driven more by environment and barrier health than by fixed biology, then part of the answer lies upstream, in prevention, in early-life exposure, and in supporting the body's own regulation, not only in treating disease once it has taken hold. That reframing is where much of the most interesting immunology is now heading.