The Real Reason Allergies Are Getting Worse: A Top Allergy Doctor Explains
Pediatric allergy specialist Prof. Adam Fox explains why allergies have surged over the past century, pointing to the skin barrier, eczema and the microbiome rather than genes alone. He also debunks the penicillin allergy myth, clarifies allergy vs intolerance, and describes how desensitization is transforming treatment.
Overview
In this ZOE conversation, Professor Adam Fox — a pediatric allergy specialist at King's College London — walks through why allergies have moved from medical curiosity to everyday reality. He lays out the data: a trebling of severe allergic reactions in the UK between 1998 and 2018, driven mainly by young children with food allergy.
He explains that we tend to become allergic to the sticky, protein-rich foods eaten around us in infancy, and that a disrupted skin barrier — often linked to eczema and the filaggrin gene — lets the immune system meet those proteins in the wrong place and misjudge them. Fox also traces the explosion of hay fever over 200 years and its real cost on exams, work and driving. A major thread is the penicillin allergy myth: about 10% of people carry the label, yet roughly 90% turn out not to be allergic when properly tested.
He argues the hygiene hypothesis is too simple and that the microbiome plays a central, if not fully understood, role, supported by mouse studies and data on diverse maternal diets. Finally, he clarifies the difference between allergy, sensitivity and intolerance, and shares his excitement about desensitization — retraining the immune system with small, increasing doses. The tone throughout is educational and wellness-oriented, not medical advice.
Key quotes
5There was a trebling in the number of people with severe allergic reactions between 1998 and 2018.
Allergy is an inappropriate immune response to something that should be ignored.
If you're a baby with eczema and that baby's immune system gets to see those proteins, that's when you're at risk of developing allergy.
It's monumentally over-diagnosed. Ninety percent of the people labeled turn out not to be allergic.
This is a paradigm shift in the way that we manage food allergies.
Key ideas
9The rise is real and measurable
Around 5% of children in the UK and US now have a food allergy. UK data show a trebling of emergency severe reactions between 1998 and 2018 and a doubling of reported food allergy between 2008 and 2018, driven mostly by young children.
A few sticky foods drive most allergy
Milk, egg, peanut, tree nuts, sesame, wheat and kiwi account for most food allergy. Peanut gets attention because it's serious and rarely outgrown, but milk is the most common cause of anaphylaxis in young children.
You react to what you grew up with
Allergy patterns follow the household diet — chickpeas and lentils in India, cashew and pistachio in British-Asian families, sesame where hummus is common. Exposure, not novelty, shapes what you become allergic to.
Skin exposure vs gut exposure decides tolerance
When an infant first meets a food protein through the gut, the immune system files it as harmless. When it meets that same sticky protein through a leaky skin barrier instead, the immune system can mistake it for a threat.
Eczema and the filaggrin gene
Eczema is a dry, itchy condition marked by a disrupted, leaky skin barrier. The filaggrin gene makes the 'cement' between skin cells; faulty copies mean a leakier barrier, more eczema, and greater food-allergy risk.
Hay fever went from rare to everywhere
In the early 19th century a physician took nine years to find 28 hay-fever cases. Today 20–30% of adults raise their hand. A shift this fast over ~200 years can't be explained by genetics alone.
The penicillin allergy myth
About 10% of people carry a penicillin-allergy label, usually from a childhood rash misattributed to the drug. When properly tested, roughly 90% are not allergic — yet the label pushes them toward worse, costlier antibiotics for life.
Beyond hygiene: the microbiome
The hygiene hypothesis has big holes. The stronger story is genetics plus eczema plus the microbiome: a more diverse gut, skin and airway microbiome is linked to fewer allergies, though cause and effect are still being untangled.
Allergy, sensitivity and intolerance differ
An allergy involves the immune system and can be dangerous; an intolerance, like lactose intolerance, does not involve the immune system and is unpleasant but not dangerous. The terms are not interchangeable.
Practical takeaways
6- 1
Question a penicillin-allergy label 41:00
Find your 'origin story' — often a childhood rash — and ask your doctor whether a proper assessment or de-labeling is worth it, so you're not stuck on second-line antibiotics for life.
- 2
Diverse diets are linked to fewer allergies 54:00
Evidence suggests a broad, diverse maternal diet and early introduction of a wide range of foods to infants is associated with fewer allergies developing.
- 3
Insist on a proper diagnosis 55:30
Skip mail-order 'allergy' blood tests. A real diagnosis combines a clinical history with a skin-prick test, specific blood test, or a supervised food challenge.
- 4
Never desensitize at home 1:00:30
Desensitization can retrain the immune system, but it carries real risk and requires close supervision — it is not a do-it-yourself treatment.
- 5
Choose non-sedating antihistamines 1:01:20
For hay fever, favor second-generation, non-sedating antihistamines like cetirizine, loratadine or fexofenadine, and avoid old sedating ones such as chlorphenamine.
- 6
Simple hay-fever habits help 1:01:00
Saline nasal sprays, a little Vaseline around the nostrils, washing hair before bed, keeping windows closed at night and not line-drying clothes can all reduce pollen exposure.
Topics & chapters
14The allergy epidemic
Why severe allergic reactions have tripled and why allergies are far from trivial.
Meet Adam Fox and quickfire answers
A pediatric allergy professor tackles rapid myths: you aren't born allergic, and most penicillin 'allergies' aren't real.
Have food allergies really increased?
From one peanut-allergic child in a school of 1,500 to today's classrooms full of EpiPens.
What the data shows
A trebling of severe reactions from 1998–2018 and a doubling of food allergy from 2008–2018, driven by young children.
Why peanut gets the headlines
A small set of foods causes most allergy; milk, not peanut, is the top fatal trigger in young children.
The geography of allergy
You tend to become allergic to whatever is eaten in your household and culture.
The skin-barrier theory
Sticky food proteins meeting a leaky infant skin barrier can teach the immune system to attack food.
Eczema and the filaggrin gene
What eczema is, why the skin leaks, and how the filaggrin gene links skin to food allergy.
Hay fever through history
From a 19th-century curiosity to 20–30% of adults today — a change too fast for genetics.
The real cost of hay fever
Dropped exam grades, lost productivity and impaired driving on sedating antihistamines.
The penicillin allergy myth
Why 10% carry the label, why ~90% aren't truly allergic, and how de-labeling works.
Hygiene hypothesis and the microbiome
Why the clean-child theory falls short and what mouse and diet studies reveal about gut bacteria.
Allergy vs intolerance vs sensitivity
Lactose intolerance, anaphylaxis, adult-onset allergy and the gluten confusion clarified.
Desensitization and the future
Retraining the immune system, sublingual immunotherapy, and why treatment has been transformed.