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Primary topic: HNMT gene histamine metabolism

HNMT Gene and Metabolism: What It Means for Your Body

HNMT handles histamine inside cells, making it relevant when histamine patterns look broader than just food reactions.

What is the HNMT gene?

HNMT breaks down histamine inside tissues using methyl groups. That links histamine handling to methylation support and intracellular clearance capacity.

How HNMT affects metabolism

If HNMT-related activity is slower, histamine signaling may persist longer inside tissues. That can influence headaches, sleep quality, irritability, and reactions that do not map only to obvious food triggers.

What happens when HNMT is altered

Altered HNMT activity does not prove a histamine problem, but it can explain why histamine-related patterns seem broader or more persistent than expected.

Curated SNP evidence for HNMT

These SNPs come from the approved study-level evidence model. Each claim is scored from curated study rows, then gated before it can influence pathway scoring.

Histamine

Evidence-backed report connection

HNMT currently has 2 curated SNPs, 6 claim-level scores, and 0 claims eligible for pathway scoring.

Open the sample report
rs1050891HNMT supporting signal3 claims · 6 study rows

expression · AG

HNMT gene expression

Not used for pathway scoring

rs1050891 AG is associated with increased HNMT gene expression.

This SNP is scored as a modest tendency toward higher HNMT expression/activity when the G allele is present.

Likely effectHigher gene expression signal
Signal sizeSmall signal
Evidence supportLimited support
Report useEvidence only, not scored
Show study evidence
Evidence 1identity only · unknownNCBI dbSNP places rs1050891 in HNMT and lists the main HNMT transcript consequence as a 3 prime UTR variant, NM_006895.3:c.*60.PMC6386932review · directA review of HNMT biology reports that the A-to-G polymorphism at nucleotide 939 in the 3 prime untranslated region increases HNMT mRNA stability, HNMT protein, and enzymatic activity. This supports a modest increased-expression tendency for G-containing genotypes.

expression · GG

HNMT gene expression

Not used for pathway scoring

rs1050891 GG is associated with increased HNMT gene expression.

This SNP is scored as a modest tendency toward higher HNMT expression/activity when the G allele is present.

Likely effectHigher gene expression signal
Signal sizeSmall signal
Evidence supportLimited support
Report useEvidence only, not scored
Show study evidence
Evidence 1identity only · unknownNCBI dbSNP places rs1050891 in HNMT and lists the main HNMT transcript consequence as a 3 prime UTR variant, NM_006895.3:c.*60.PMC6386932review · directA review of HNMT biology reports that the A-to-G polymorphism at nucleotide 939 in the 3 prime untranslated region increases HNMT mRNA stability, HNMT protein, and enzymatic activity. This supports a modest increased-expression tendency for G-containing genotypes.

expression · AA

HNMT gene expression

Not used for pathway scoring

rs1050891 AA has no scored directional claim for HNMT gene expression.

This SNP is scored as a modest tendency toward higher HNMT expression/activity when the G allele is present.

Likely effectNo clear expression signal
Signal sizeMinimal signal
Evidence supportVery limited support
Report useEvidence only, not scored
Show study evidence
Evidence 1identity only · unknownNCBI dbSNP places rs1050891 in HNMT and lists the main HNMT transcript consequence as a 3 prime UTR variant, NM_006895.3:c.*60.PMC6386932review · directA review of HNMT biology reports that the A-to-G polymorphism at nucleotide 939 in the 3 prime untranslated region increases HNMT mRNA stability, HNMT protein, and enzymatic activity. This supports a modest increased-expression tendency for G-containing genotypes.
rs11558538Thr105Ile3 claims · 6 study rows

enzyme activity · CT

HNMT enzyme activity

Not used for pathway scoring

rs11558538 CT is associated with reduced HNMT enzyme activity.

This SNP is scored as a tendency toward lower HNMT histamine-methylation activity when the T allele is present.

Likely effectLower enzyme activity signal
Signal sizeSmall signal
Evidence supportLimited support
Report useEvidence only, not scored
Show study evidence
Evidence 1identity only · unknownNCBI dbSNP lists rs11558538 in HNMT as a C>T missense variant, NM_006895.3:c.314C>T, producing p.Thr105Ile in histamine N-methyltransferase.PMC6386932review · close proxyA review of HNMT in the brain describes the C314T change as replacing threonine with isoleucine at codon 105 and reports that this change leads to decreased HNMT enzymatic activity. This supports a lower-activity tendency for T-containing genotypes, with a larger score for two T copies.

enzyme activity · TT

HNMT enzyme activity

Not used for pathway scoring

rs11558538 TT is associated with reduced HNMT enzyme activity.

This SNP is scored as a tendency toward lower HNMT histamine-methylation activity when the T allele is present.

Likely effectLower enzyme activity signal
Signal sizeSmall signal
Evidence supportLimited support
Report useEvidence only, not scored
Show study evidence
Evidence 1identity only · unknownNCBI dbSNP lists rs11558538 in HNMT as a C>T missense variant, NM_006895.3:c.314C>T, producing p.Thr105Ile in histamine N-methyltransferase.PMC6386932review · close proxyA review of HNMT in the brain describes the C314T change as replacing threonine with isoleucine at codon 105 and reports that this change leads to decreased HNMT enzymatic activity. This supports a lower-activity tendency for T-containing genotypes, with a larger score for two T copies.

enzyme activity · CC

HNMT enzyme activity

Not used for pathway scoring

rs11558538 CC has no scored directional claim for HNMT enzyme activity.

This SNP is scored as a tendency toward lower HNMT histamine-methylation activity when the T allele is present.

Likely effectNo clear enzyme signal
Signal sizeMinimal signal
Evidence supportVery limited support
Report useEvidence only, not scored
Show study evidence
Evidence 1identity only · unknownNCBI dbSNP lists rs11558538 in HNMT as a C>T missense variant, NM_006895.3:c.314C>T, producing p.Thr105Ile in histamine N-methyltransferase.PMC6386932review · close proxyA review of HNMT in the brain describes the C314T change as replacing threonine with isoleucine at codon 105 and reports that this change leads to decreased HNMT enzymatic activity. This supports a lower-activity tendency for T-containing genotypes, with a larger score for two T copies.

Common symptoms people report

  • headaches or irritability after higher histamine load
  • sleep disruption tied to histamine-like symptoms
  • flushing or skin reactivity not fully explained by diet
  • feeling more reactive during stress or inflammation

Biomarkers to validate

Symptom and trigger log

Still the most practical first-pass validation tool.

Homocysteine

Useful because HNMT uses methylation support.

Nutrient status for B vitamins

Adds context when methylation and histamine overlap.

Where DNA analysis helps

DNA can show that intracellular histamine handling may deserve more attention than food-only explanations suggest. It helps focus validation when symptoms are diffuse.

Example Insight

Your intracellular histamine-handling pathway may rely more heavily on methylation support than average.

Suggested validation: homocysteine plus histamine-trigger tracking.

What to do next

  • Look at histamine patterns together with methylation markers.
  • Compare HNMT with DAO and MTHFR when reactivity feels multi-factorial.
  • Use symptom tracking before attributing every issue to histamine.

Upload your DNA file and receive a structured metabolic pathway analysis with prioritized insights and suggested validation markers.

Get My DNA Report

Related pages

DAO

DAO gene histamine metabolism

MTHFR

MTHFR gene metabolism

Choline status

choline status and methyl donor support

Cysteine, sulfate, and transsulfuration

Cysteine, sulfate, and transsulfuration DNA follow-up

B12 transport and recycling pathway

B12 transport and recycling pathway

Choline and phosphatidylcholine pathway

choline and phosphatidylcholine pathway

Can DNA predict metabolism?

can DNA predict metabolism

23andMe vs Metastate metabolism report

23andMe vs Metastate metabolism report

Related symptom angle

Histamine intolerance genetics

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