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Gene & pathway reference · FROM DR. PURSER’S TEACHING

HDC

HDC is the gene name for Histidine Decarboxylase. Learn what a specific result could mean and what to ask about it.

Based on teaching by Dan Purser, MD. How we prepare these guides

Updated Sep 23, 2026 · Educational reference

THE TEACHING CONNECTION

Histamine production is one part of the circuit

Histamine production is one part of the circuit

HDC is involved in the enzyme step converting histidine to histamine. This is the production side of the circuit, separate from AOC1-mediated clearance and the HRH1/HRH2 receptors that receive histamine signals.

Putting the pieces together

The reference discusses dietary patterns and clinician-selected antihistamine approaches in this section. These are different mechanisms, not a recommendation to combine treatments from every gene page. Symptoms and response history need clinical interpretation; a gene listing is not a diagnosis of MCAS.

Where the VARS Triad and MTHFR Daily fit

If you are exploring homocysteine or cytokines, Dr. Purser may discuss MTHFR Daily and the VARS Triad: VARS Glutathione, VARS SOD, and VARS Catalase. He gives glutathione a central place in his approach to antioxidant support.

A gene result alone cannot tell you that you need these products or that they will treat a condition. Review your current results, medicines, goals, and tolerance with your clinician before choosing a product or dose.

A question to bring to your visit

Which part of the histamine circuit are we evaluating, and does my symptom history support that interpretation?

Reading your own results

Bring your original report, current results, health history, and medicines to your visit. This information can help you ask questions, but it cannot diagnose a condition or choose a supplement dose for you.

Variant lookup

These names can help you find an entry on your original genetic report. Seeing a name here does not tell you whether it affects your health or whether you need treatment.

Names you may see

Histidine Decarboxylase