The Link: Allergies, Histamine & Neurodivergence
Many parents of children with ADHD or autism (ASD) may notice that their child also struggles with allergies, skin rashes, food sensitivities, or asthma. It turns out, this is more than just coincidence. Science is beginning to show that there may be a link between neurodivergence and immune system responses—especially those involving histamine.
Let’s get into this a bit more…
What Is Histamine?
Histamine is a chemical your body releases during an allergic reaction. It causes symptoms like:
- Itchy or watery eyes
- Sneezing or runny nose
- Hives or eczema
- Swelling
- Asthma or wheezing
- Tummy troubles in some cases
Histamine helps your body fight off allergens (like pollen or mould), but in sensitive kids, it can be overactive, leading to frequent flare-ups.
What’s the Link With Neurodivergent Kids?
Scientific research increasingly suggests a biological link between neurodevelopmental conditions like ASD and ADHD and immune system dysregulation. Several studies have found higher rates of allergic diseases among children with autism and ADHD compared to neurotypical peers.
Scientists believe this could be due to a few factors:
- Immune system differences: Some children with ADHD or autism have overactive immune responses or chronic low-grade inflammation.
- Mast cell activation: Mast cells release histamine. In some neurodivergent children, these cells may be more active, even in the brain, which could contribute to sensory sensitivity, anxiety, or hyperactivity.
- Genetics and gut health: Family history, gut bacteria imbalances, and environmental exposures may also play a role.
A large study published in Scientific Reports in 2021 found that children with ADHD or autism were significantly more likely to have allergies, including eczema, food allergies, and hay fever.
How Do Allergies Show Up?
Allergies can appear in many different ways:
- Skin: Eczema, hives, or unexplained rashes
- Breathing: Chronic stuffy nose, sneezing, wheezing
- Digestive: Bloating, diarrhoea, reflux
- Behaviour: Irritability, fatigue, hyperactivity, sleep problems
You might also notice behaviour changes after eating certain foods or being in particular places (like around animals or during springtime).
Common Allergens Include:
- Food: Dairy, gluten, eggs, peanuts, soy, shellfish
- Environmental: Mould, pollen, dust mites, pet dander
- Chemical or contact: Fragrances, detergents, metals like nickel
Can Antihistamines Help with ADHD or Autism Symptoms?
This is a question more parents (and doctors) are asking.
Since histamine affects not only the immune system but also brain function—like sleep, alertness, and emotion—some children may benefit from antihistamines beyond allergy relief.
Possible Benefits:
- Improved sleep: Some sedating antihistamines (like hydroxyzine) can help with falling and staying asleep.
- Reduced anxiety or sensory overload: Certain antihistamines may calm the nervous system.
- Less hyperactivity: In children with allergy-related behaviours, antihistamines may ease symptoms.
But they don’t work for everyone. Some antihistamines can actually cause hyperactivity or agitation in young children. Always speak to a doctor before trying anything new.
If you notice that your child’s mood or behaviour improves on antihistamines, it may be worth investigating underlying allergies or sensitivities further.
What Should You Do if You Suspect an Allergy?
If you think allergies might be affecting your child, here are the steps to take:
- Track symptoms
Keep a diary of flare-ups—note food, environmental triggers, or times of day. - Talk to your GP
Ask for a referral to an allergist or paediatric immunologist. - Get tested
- Skin prick test: A tiny amount of allergen is placed on the skin to see if there’s a reaction.
- Blood test (specific IgE): Checks immune response to allergens.
- Patch testing: Used for delayed reactions like eczema.
- Oral food challenge: Done under medical supervision to confirm food allergies.
Treatment Options
Once an allergy is identified, treatment may include:
- Antihistamines: Reduce sneezing, itching, rashes, or mild asthma symptoms.
- Nasal sprays and inhalers: Help with breathing issues like hay fever or asthma.
- Topical creams: For eczema and skin flare-ups.
- Mast cell stabilisers: May help children with more complex immune reactions.
- Dietary changes: A supervised elimination diet can help pinpoint food triggers.
- Environmental changes: Use air filters, reduce dust, check for mould, and wash bedding regularly.
Long-Term Options
- Allergy immunotherapy: Allergy shots or sublingual tablets that gradually build tolerance to allergens over time.
- Probiotics and gut support: The gut plays a huge role in immunity and may affect both allergic and behavioural symptoms.
- Integrative or functional medicine: Some families choose to explore root-cause approaches to chronic allergy and immune issues.
If your child has ADHD or autism and also shows signs of allergies, it’s worth investigating. Managing allergies can lead to improvements in sleep, focus, mood, and overall wellbeing.
While there’s no “cure” for neurodivergence—and nor should there be—supporting the body’s immune system can make life a little easier for your child and your family.
References
- Theoharides, T.C., et al. (2015). Mast Cells and Inflammation. Biochimica et Biophysica Acta, 1822(1), 21–33.
- Chang, Y.S., et al. (2021). Association of allergic diseases with ADHD and autism: A population-based study. Scientific Reports, 11, 18108.
- Hsiao, E.Y. (2014). Immune dysregulation in autism spectrum disorder. International Review of Neurobiology, 113, 269–302.
- Pelsser, L.M., et al. (2011). Effects of a restricted elimination diet on the behaviour of children with ADHD. The Lancet, 377(9764), 494–503.
- DeVito, T.J., & Biesbroek, S. (2022). Mycotoxins and cognitive functioning: A scoping review. Toxins, 14(9), 615.
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