What If Your Allergies and Your ADHD Are the Same Thing?

A 2023 paper revisited a forgotten 1950s syndrome and the implications for people with ADHD are genuinely remarkable. It all comes down to one molecule you've probably never connected to your brain

Most people with ADHD know about dopamine. Some know about noradrenaline. But almost nobody is talking about histamine and if this research is right, that needs to change. A 2023 paper in the Journal of Clinical Medicine made a bold argument: that a syndrome first described in the 1950s which doctors thought was an allergy condition, was probably describing ADHD all along. And the reason both conditions exist together so often? A single enzyme that most people have never heard of

First, a bit of history

In 1954, an American allergist called Frederick Speer described what he called the "Allergic Tension-Fatigue Syndrome" (SATFS). He was writing about patients who had allergies but alongside the sneezing and the rashes, they also showed something else: a very particular pattern of behaviour

1954: Speer describes SATFS Patients with allergies showing restlessness, distractibility, hyperactivity, fatigue, headaches, muscle tension, and sleep problems. He called it a "primary allergic disorder of the nervous system."

1960: ADHD is named

Stella Chess formally names and describes Attention Deficit Disorder. The description looks remarkably familiar

2023: The paper asks: were these the same people?

Researchers revisit Speer's work and argue he was probably describing ADHD patients with allergic comorbidity six years before ADHD even had a name

Look at the overlap in symptoms, it's hard to argue with

SPEER'S SATFS (1954)	ADHD (AS WE KNOW IT)
✓ Hyperactivity / restlessness ✓ Distractibility ✓ Insomnia & sleep problems ✓ Chronic fatigue ✓ Headaches ✓ Muscle tension ✓ Irritability & mood swings	✓ Hyperactivity / restlessness ✓ Inattention & distractibility ✓ Sleep difficulties ✓ Fatigue & capacity crashes ✓ Migraines (high comorbidity) ✓ Physical tension & dysregulation ✓ Emotional dysregulation / RSD

So what's the missing link? Histamine.

Here's where it gets really interesting. You probably know histamine as the thing that gives you hay fever or makes you reach for antihistamines. But histamine isn't just an allergy chemical, it's also a neurotransmitter. It works in your brain

What Histamine actually does

In your body: histamine drives allergic responses, inflammation, swelling, sneezing, itching. In your brain: histamine regulates wakefulness, attention, and arousal. It projects into regions involved in focus and executive function. Think of it as your brain's "alertness signal." When histamine signalling goes wrong, both your immune system and your attention are affected, at the same time, through the same molecule.

"Histamine isn't just what makes you sneeze. It's also a key signal your brain uses for attention and arousal. Too much of it, or the wrong kind, and both your body and your brain feel it."

The enzyme you've probably never heard of: DAO

The paper's central argument is about an enzyme called diamine oxidase (DAO). DAO's job is to break down histamine in the body. When DAO is working well, excess histamine gets cleared. When it isn't, histamine builds up. And the research suggests that DAO deficiency may be closely linked to ADHD.

Not because of some far-fetched mechanism, but because when histamine accumulates:

• Your immune system overreacts, producing allergy-like symptoms, inflammation, sensitivities to foods, skin reactions

• Your brain's attention and arousal systems are dysregulated, affecting focus, wakefulness, and how well your prefrontal cortex (your planning, organising brain) can function

• Both things happen simultaneously, because it's the same molecule causing both

  
  

This also explains why antihistamines, the tablets people take for hay fever, are known to cause brain fog and cognitive dulling. They're blocking histamine in your brain as well as your body. For someone with ADHD whose histamine system is already dysregulated, that's significant

What this means if you have ADHD

This is a conceptual paper, not a clinical trial, so it's not a diagnosis or a treatment protocol. But it does reframe something important: the cluster of physical symptoms that so many people with ADHD experience may not be random coincidences.

The high rates of ADHD alongside allergies, eczema, asthma, migraines, gut issues, and food sensitivities? This research suggests they may share a common biological root, not just overlap by chance

What's worth paying attention to

Notice your body patterns alongside your ADHD patterns.

Do your cognitive crashes correlate with allergy flare-ups? Do certain foods particularly high-histamine ones like aged cheese, wine, fermented foods, or processed meats, seem to worsen your focus or mood?

Be cautious with antihistamines.

If you regularly take them for hay fever or allergies, it's worth knowing they cross the blood-brain barrier and affect attention. Newer antihistamines are designed to do this less, worth discussing with your GP.

DAO deficiency is being researched.

DAO supplements and low-histamine dietary approaches are an emerging area. This is early territory but if you have significant gut symptoms alongside ADHD, it may be worth raising with a knowledgeable practitioner

Your body and brain are one system.

ADHD is not just a brain condition happening in isolation. Research like this is pointing toward ADHD as something that shows up across multiple systems in the body, immune, neurological, hormonal. The tiredness, the physical sensitivity, the gut stuff, it all belongs in the picture

The bigger takeaway

What's striking about this paper isn't just the science, it's the validation. Speer's patients in the 1950s were showing up with fatigue, tension, distractibility, and reactivity.

They were being seen as allergic patients with behavioural quirks. We now understand them as people with ADHD, whose immune and neurological systems were operating in the same dysregulated state, driven, possibly, by the same molecule.

If you've spent years wondering why your hay fever always arrives alongside a particularly bad ADHD week, or why your brain feels like it's wrapped in cotton wool every time you're fighting a reaction, this is not in your head. It might just be histamine.

Based on: Blasco-Fontecilla H. Is Histamine and Not Acetylcholine the Missing Link between ADHD and Allergies? Speer Allergic Tension Fatigue Syndrome Re-Visited. Journal of Clinical Medicine, 2023. This is informational content, please speak with a healthcare professional before making changes to any treatment or diet. Written by Charlotte Fry, ADHD Coach at Elephant in the Mind