Histamine, ADHD and Perimenopause: Why Hay Fever Season Affects Us Differently

My eyes are streaming, I can't stop sneezing, and I'm paying for every minute of this beautiful weather.

Hay fever season is here. And if you have ADHD, it doesn't just affect your eyes and nose.

There's a reason pollen season can leave some of us feeling like we've lost our brains entirely. It's not just the antihistamines making you drowsy, though that's a real factor. Histamine itself is doing something in your brain. It always has been. Understanding the connection between histamine, ADHD and perimenopause changes the way you read your own experience.

Histamine Isn't Just an Allergy Response

Histamine gets blamed for allergic reactions. The itchy eyes, the runny nose. That's part of the story. But histamine is also a neurotransmitter.

It plays a direct role in attention, wakefulness, dopamine regulation, and executive function. Histamine H3 receptors modulate the release of dopamine and other key neurotransmitters in the prefrontal cortex. That's the part of the brain responsible for focus, impulse control, emotional regulation, and decision-making (Alhusaini et al., 2022). When histamine levels rise, as they do during pollen season, the systems that are already stretched in an ADHD brain can become significantly harder to manage.

For women with ADHD, that disruption isn't subtle. Concentration takes a hit and emotional dysregulation worsens. The brain fog that's already part of daily life shifts into something harder to push through.

There's also research looking at the enzyme that breaks histamine down in the body, called diamine oxidase (DAO). A 2023 study found that the majority of children with ADHD showed signs of DAO deficiency, meaning their bodies weren't clearing histamine efficiently. This suggests the histamine-ADHD connection may be more significant than most clinicians currently recognise (Blasco-Fontecilla, 2023).

Hay fever doesn't cause ADHD. But there's a real reason certain times of year can make ADHD symptoms considerably worse, and it's worth understanding why.

Why Perimenopause Makes This Even Harder

Oestrogen and histamine are closely linked. Oestrogen promotes the release of histamine and amplifies the immune response to allergens, while fluctuating oestrogen levels affect how well the body regulates histamine (Fan et al., 2019). Research on sex hormones and allergic responses has found that women, particularly during periods of hormonal flux, are more vulnerable to histamine-driven reactions than men, and that this vulnerability intensifies as oestrogen becomes unpredictable (Gutiérrez-Brito et al., 2025).

This is one of the reasons some women find that allergies get worse during perimenopause. It's also why the brain fog deepens and the emotional reactivity worsens during hay fever season when you're already navigating perimenopause with ADHD. The strategies that used to help seem to stop working entirely.

None of these systems are operating separately. When one becomes unstable, the others are affected.

Mast Cells, Inflammation and Neurodivergence

There's emerging research on the role of mast cells in neurodivergence.

Mast cells are part of the immune system and are responsible for triggering histamine release. They're found throughout the body, including in the brain. Research has begun to investigate whether mast cell activation may play a role in how neurodivergent brains respond to stress and inflammation, with some researchers suggesting that heightened inflammatory responses may be more closely connected to neurodivergent neurological wiring than previously understood (Theoharides, Kavalioti and Tsilioni, 2019; Kovacheva et al., 2024).

This research is still early, particularly in relation to ADHD and perimenopause. But it points toward something many women already know in their own bodies: that the immune system and the brain are not operating independently of each other, and that hormones are part of that conversation too.

What This Means For You

Understanding what's happening in your body doesn't make hay fever season easier. But it does change your relationship to it.

If your concentration has been harder to find and your emotional reactivity higher than usual during pollen season, you're not imagining it and you're not doing it wrong. You're managing more than most people realise, with a nervous system that's doing its best under compounding pressure.

That is worth knowing. And it's worth telling the women around you who are wondering why they're struggling so much more than everyone else.

References

Alhusaini, M., Eissa, N., Saad, A.K., Beiram, R. and Sadek, B. (2022) 'Revisiting preclinical observations of several histamine H3 receptor antagonists/inverse agonists in cognitive impairment, anxiety, depression, and sleep-wake cycle disorder', Frontiers in Pharmacology, 13, article 861094. doi: 10.3389/fphar.2022.861094.

Blasco-Fontecilla, H. (2023) 'Histamine and ADHD', Journal of Clinical Medicine, 12(16), article 5350. doi: 10.3390/jcm12165350.

Fan, Z., Che, H., Yang, S. and Chen, C. (2019) 'Estrogen and estrogen receptor signaling promotes allergic immune responses: effects on immune cells, cytokines, and inflammatory factors involved in allergy', Allergologia et Immunopathologia, 47(5), pp. 506-512. doi: 10.1016/j.aller.2019.03.001.

Gutiérrez-Brito, J.A., Lomelí-Nieto, J.Á., Muñoz-Valle, J.F., Oregon-Romero, E., Corona-Angeles, J.A. and Hernández-Bello, J. (2025) 'Sex hormones and allergies: exploring the gender differences in immune responses', Frontiers in Allergy, 5, article 1483919. doi: 10.3389/falgy.2024.1483919.

Kovacheva, E., Bhatt, D.L. and Theoharides, T.C. (2024) 'Mast cells in autism spectrum disorder', International Journal of Molecular Sciences, 25(5), article 2651. doi: 10.3390/ijms25052651.

Theoharides, T.C., Kavalioti, M. and Tsilioni, I. (2019) 'Mast cells, stress, fear and autism spectrum disorder', International Journal of Molecular Sciences, 20(15), article 3611. doi: 10.3390/ijms20153611.