ADHD & allergies: The link

ADHD and Allergies: How are they linked?

There are several possible causal links between ADHD and allergies.

• Immune system and the brain. Allergies trigger inflammation that reaches the brain, and stress worsens both ADHD and allergy symptoms.
• Genetics. Some research suggests children are more likely to develop ADHD if their mother has allergies.
• Histamine. This chemical can impact focus and mood.
• Sleep. Both ADHD and allergies commonly disrupt sleep, which can worsen symptoms.
• Diet. A poor diet, high in processed foods, can worsen inflammation and cause nutritional deficiencies.

Does your immune system affect your brain?

Allergies are essentially an overactive immune response to things like pollen that are normally harmless. This can cause sneezing, a runny nose, itching, and, in severe cases, anaphylaxis.

When you have an allergic reaction, your immune system releases chemicals that cause inflammation to ‘fight off’ the threat.¹ This inflammation may reach your brain, affecting the parts responsible for memory, learning, thinking and emotions. Studies have shown that high levels of inflammation are associated with ADHD.²

If you have ADHD, you might also experience high stress levels. Stress can disrupt the way your immune system works.³ This can lead to imbalanced hormone levels and even higher stress levels,² which can make ADHD and allergy symptoms worse.⁴

There isn’t a lot of direct research linking ADHD, allergies, and inflammation. But it’s believed to be a contributing factor for both conditions.

Histamine and neurotransmitters

Histamine is a chemical that influences mood, sleep, and focus. It’s one of the main components in an allergic response. It’s also important for focus and attention.

Studies show that high levels of histamine in the body can lead to ADHD symptoms, but low levels of histamine in the brain can worsen ADHD symptoms as well.⁵

This may seem contradictory, but the role of histamine depends on its location.

Too little histamine in the brain may cause ADHD-like symptoms, but too much histamine in the body can worsen ADHD because of inflammation and allergic reactions.

The body and brain make histamine differently, so extra histamine from the body can’t reach the brain.

Can your genes play a role?

There may be a genetic link between ADHD and allergies.

Epigenetic changes are differences in how genes work due to the environment.

One study found that children were more likely to develop ADHD if their mothers had allergies. The risk was even higher for girls.⁶

There may also be other genetic links between ADHD and allergies, such as:⁶

• Problems with how cells make energy (mitochondrial dysfunction)
• Problems with how the brain uses serotonin (which affects mood and focus)
• Inflammation in the body

Sleep disruption

Sleep problems are common in both conditions. Around 57% of adults and 88% of children with allergies⁸ have sleep disturbances, as do 50-75% of adults with ADHD.⁹

Allergies can disrupt sleep because of nose congestion, itching and discomfort. This lack of sleep can then worsen allergy symptoms.⁷

Similarly, ADHD can make it difficult to fall asleep, and less sleep can further worsen ADHD symptoms.

Studies have found that poor sleep worsens ADHD symptoms in children.¹⁰

It’s not clear if sleep problems cause ADHD and allergies, or if ADHD and allergies cause sleep problems. But one thing is clear: people with either condition often have trouble sleeping.

Nutritional deficiencies and diet

Your diet can affect the development of both conditions. A diet that's high in refined, processed, sugary and fatty foods can be linked to wheezing in children, and also make them more likely to develop food allergies.⁶

Likewise, a poor diet can worsen ADHD symptoms and may also contribute to the development of ADHD.¹¹

A poor diet can also cause inflammation and lead to nutritional deficiencies. This can dysregulate the way the gut and brain interact with each other, affecting digestion, mood and brain.¹⁰

Allergies can impact gut health and alter the gut microbiome (the community of microorganisms that live inside your body). This can increase the risk of mood disorders and contribute to the development of ADHD.¹²

References 

1. Ogulur, I., et al. (2021). Advances and highlights in biomarkers of allergic diseases. Allergy, 76(12), 3659.

2. Saccaro, L. F., et al. (2021). Inflammation, Anxiety, and Stress in Attention-Deficit/Hyperactivity Disorder. Biomedicines, 9(10), 1313.

3. Du, J., et al. (2025). Exploring the complex relationship between attention deficit hyperactivity disorder and the immune system: A bidirectional Mendelian randomization analysis. Journal of Affective Disorders, 369, 854-860.

4. Priftis, K.N. and Anthracopoulos, M.B. (2008). The causal relationship between stress and asthma. Allergologia et Immunopathologia, 36(6), pp.343–346.

5. Blasco-Fontecilla, H. (2023). Is Histamine and Not Acetylcholine the Missing Link between ADHD and Allergies? Speer Allergic Tension Fatigue Syndrome Re-Visited. Journal of Clinical Medicine, 12(16), 5350.

6. Yi Chua, R. X., et al. (2021). Understanding the Link Between Allergy and Neurodevelopmental Disorders: A Current Review of Factors and Mechanisms. Frontiers in Neurology, 11, 603571.

7. Xi, Y., et al. (2022). Allergy-related outcomes and sleep-related disorders in adults: A cross-sectional study based on NHANES 2005–2006. Allergy, Asthma, and Clinical Immunology: Official Journal of the Canadian Society of Allergy and Clinical Immunology, 18, 27.

8. Allergy UK (2022). Statistics and Figures. [online] Allergy UK | National Charity.

9. Ives, L. (2024). ADHD and sleep problems: the complete guide. [online] The Telegraph.

10. Lin, Y., et al. (2016). Associations between allergic diseases and attention deficit hyperactivity/oppositional defiant disorders in children. Pediatric Research, 80(4), 480-485.

11. Pinto, S., et al. (2022). Eating Patterns and Dietary Interventions in ADHD: A Narrative Review. Nutrients, 14(20), 4332.

12. Cickovski, T., et al. (2023). Attention Deficit Hyperactivity Disorder (ADHD) and the gut microbiome: An ecological perspective. PLOS ONE, 18(8), e0273890.