04/27/2026
HNMT (Histamine N-Methyltransferase) is responsible for breaking down histamine inside cells, especially in the brain, nervous system and airways.
While DAO handles breaking down histamine from food in the gut… HNMT handles histamine internally. This is the kind that affects your mind and mood, and it's responsible for clearing histamine from your body.
When this gene isn’t working efficiently, histamine can build up inside the body. This can look like:
Anxiety or feeling “on edge”
Racing thoughts at night
Insomnia (especially waking between 2–4am)
Headaches or migraines
Sensitivity to smells, foods, or environments
Chronic congestion or asthma-like symptoms
Basically… your nervous system feels like it’s stuck in overdrive.
HNMT relies heavily on methylation to do its job. So if you have:
MTHFR mutations
High histamine symptoms
Poor stress tolerance
…there’s often a methylation bottleneck affecting HNMT.
If taking anti-histamines or a low histamine diet doesn’t affect your symptoms, it may be your body’s ability to process and clear it that's the issue.
Your genetics can be a BIG piece of that puzzle. ✨