Scombroid poisoning: causes, symptoms and treatment

Scombroid poisoning is a form of food poisoning. This happens when a person eats fish that contains large amounts of a chemical called histidine.

Histidine is an amino acid found naturally in fish. When people don’t keep fish in the refrigerator, bacteria break down histidine and convert it into histamine.

According to the American Academy of Allergy, Asthma, and Immunology (AAAAI), histamine is responsible for the toxicity that causes scombroid poisoning.

When a person consumes large amounts of histamine-laden fish, they experience symptoms resembling an allergic reaction, such as hives. However, according to the National Capital Poison Control Center, this is not a true allergy to a specific fish.

The condition is usually not long or severe. Food and Drug Administration (FDA). Mild cases often go away on their own without treatment, but some people may benefit from antihistamines.

A person experiencing severe symptoms such as chest pain or trouble breathing should go to the emergency room or call local emergency services.

Keep reading to learn more about the causes, symptoms, treatment, prevention, and outlook for scumbroid poisoning.

Scombroid poisoning is caused by eating certain types of fish that have gone bad. According to the Centers for Disease Control and Prevention (CDC), the most common types of fish are:

  • tuna
  • mackerel
  • bluefish
  • mahi mahi or dolphin fish
  • herring
  • sardine
  • amberjack
  • anchovies
  • marlin

According to the AAAAI, this fish is high in the chemical histidine.

When people do not store fish in the refrigerator, it leads to an overgrowth of bacteria. The bacterial strains responsible for the condition produce enzymes that convert histidine to histamine.

These strains include strains present in the skin and intestines of fish, according to 2012 studysuch as:

  • coli
  • morganella wink
  • Pseudomonas aeruginosa
  • klebsiella variety

When a person eats fish that is high in histamine, their symptoms resemble those of an allergic reaction. Because of this association with histamine, scombroid poisoning is also referred to as histamine toxicity.

People with low levels of the enzyme diamine oxidase are more likely to experience scombroid poisoning, according to the AAAI. This enzyme breaks down histamine from food. Thus, a person with a low level of the enzyme may not break down histamine as well as a person with a higher level.

The poisoning is not related to allergies, so it is safe to eat fish again if it has been refrigerated.

Symptoms usually begin within minutes to 2 hours after eating the fish. Food and Drug Administration. The initial ones resemble an allergic reaction, for example:

  • sweating
  • redness of the face
  • peppery taste in throat and mouth
  • Headache
  • dizziness
  • nausea

These initial symptoms may progress to:

  • rash on the face
  • swelling
  • hives
  • short-term abdominal pain and diarrhea

According to the FDA, symptoms usually last for 4 to 6 hours and rarely last more than 1 to 2 days.

Doctors often make a diagnosis based on circumstances, according to the AAAAI. For example, a person’s symptoms may coincide with an outbreak that affected several people who ate fish bought from the same place.

Treatment depends on the severity of the scombroid poisoning. Mild cases often disappear quickly without treatment. Some people with this condition may benefit from antihistamines such as diphenhydramine (Benadryl).

Severe cases require a trip to the emergency room. Here, treatment may include intravenous fluids, oxygen, and other medications.

Signs of a severe case include:

  • chest pain
  • labored breathing
  • swelling of the tongue and mouth

If a person has severe, non-life-threatening symptoms, it is best to see an allergist. They can help determine if a person is having an allergic reaction to fish or scumbroid poisoning.

Since scumbroid poisoning is not a true allergic reaction, does not require epinephrine injections or corticosteroids. It is also not an infection, so antibiotics are not needed.

When a person catches their own fish, the only reliable way to prevent scombroid poisoning is to store the fish in the refrigerator at or below 40°F (4°C). Cooking or freezing fish will not get rid of the histamine that causes symptoms.

If a person eats fish in a restaurant, it is impossible to determine whether it is spoiled. As a rule, it has no noticeable smell or taste. However, according to the CDC, a salty, spicy, or pungent taste can act as a red flag for histamine-induced spoilage.

Also, if someone gets scombroid poisoning in a restaurant or fish market, they must report it to the health authorities for investigation. Removing fish from the market will prevent further outbreaks from the source.

Scombroid poisoning results from eating certain types of fish, such as tuna and mackerel, that have been spoiled. Early symptoms may include facial flushing and sweating, while later symptoms may include hives and short-term diarrhea.

Although the symptoms resemble allergies, this condition is not a true allergic reaction to a specific fish. Fish can be eaten again if it hasn’t gone bad.

Treatment depends on the severity. Mild cases often go away on their own. Some people may benefit from antihistamines such as diphenhydramine (Benadryl).


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