What is Histamine?

Kelolalaut.com Histamine is a biogenic amine – a natural compound formed when bacteria break down the amino acid histidine (abundant in fish). It acts as a chemical messenger in the human body, but in food it can be dangerous if consumed in high amounts.

How is Histamine Produced in Fish?

• Certain bacteria (e.g., Morganella morganii, Klebsiella, Hafnia, Enterobacter) convert histidine → histamine.
• Happens when fish are stored at unsafe temperatures after being caught.
• Common in scombroid fish (tuna, mackerel, sardine, anchovy) → condition often called scombroid poisoning.

Histamine Poisoning (Scombroid Poisoning)
Symptoms appear quickly (minutes to hours after eating contaminated fish):

• Flushing of skin, rash
• Headache, dizziness
• Burning/tingling in mouth
• Nausea, vomiting, diarrhea
• In severe cases: low blood pressure, breathing difficulties

Safe vs Dangerous Levels

• Safe: Below 50 mg/kg of fish flesh (generally harmless).
• Suspicious: 50–200 mg/kg.
• Toxic/Dangerous: Above 200 mg/kg → can cause poisoning.

(EU & FDA regulations usually set 100 mg/kg as the maximum acceptable limit in fish products.)

How to Prevent Histamine Formation

• Rapid chilling: Ice fish immediately after catch (≤4°C).
• Proper storage: Keep cold chain unbroken from catch to processing.
• Hygienic handling: Reduce bacterial contamination.
• Testing: Use rapid test kits or HPLC methods in fish processing industries.

Key Point: Histamine is not destroyed by cooking, smoking, or canning → prevention must happen before spoilage, not after.

1. Biological Reaction of Histamine in the Body

Histamine works by binding to specific receptors on cells → triggering different reactions depending on receptor type.

Histamine Receptor Reactions

• H1 receptor
  • Location: Smooth muscle, endothelium, CNS.
  • Reaction: Allergic symptoms → vasodilation, itching, swelling, bronchoconstriction (asthma-like symptoms).
• H2 receptor
  • Location: Stomach lining, heart.
  • Reaction: Increases gastric acid secretion, faster heart rate.
• H3 receptor
  • Location: Nervous system.
  • Reaction: Controls release of neurotransmitters (histamine, dopamine, norepinephrine).
• H4 receptor
  • Location: Bone marrow, white blood cells.
  • Reaction: Regulates inflammation & immune cell movement.

That’s why histamine is linked to allergies, stomach acid, inflammation, and even brain activity.

2. Chemical Reaction of Histamine Formation

• Histamine is produced from the amino acid histidine.
• Enzyme: Histidine decarboxylase.
• Reaction: The chemical reaction of histamine formation is the decarboxylation of the amino acid L-histidine, a one-step process catalyzed by the enzyme L-histidine decarboxylase (HDC). This reaction involves the removal of a carboxyl group (-COOH) from histidine, which is released as carbon dioxide

This reaction is what happens in bacteria-contaminated fish or inside the human body (mast cells & basophils).

3. Immune Reaction (Allergic Response)

• Allergen (e.g., pollen, food, fish toxin) triggers mast cells.
• Mast cells release histamine.
• Histamine binds to receptors → causes redness, itching, swelling, mucus, stomach upset, or even anaphylaxis.
• In food → histamine forms by bacterial action on histidine.
• In the body → histamine is released by immune cells, causing allergy & inflammation reactions.

Fish Species Most at Risk

Histamine is most common in dark-meat fish from the Scombridae and Scomberesocidae families:

• Tuna
• Mackerel
• Sardine
• Anchovy
• Bonito
• Herring

How Histamine Forms in Fish

• Catch → Fish not chilled immediately.
• Bacteria multiply (e.g., Morganella, Klebsiella, Enterobacter).
• Bacteria use the enzyme histidine decarboxylase.
• Histidine → Histamine builds up in flesh.

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