Mussel Poisoning – Causes, Symptoms & Treatment

Mussel poisoning

Medicine understands mytilism as shellfish poisoning . In addition to the gastrointestinal tract, symptoms can also appear in the nervous system and on the skin. Treatment for mussel poisoning is symptomatic, as there are no antidotes.

What is mussel poisoning?

Mytilism is poisoning caused by eating shellfish. This mussel poisoning can be divided into four different forms:

  • central nervous form
  • neurotoxische Form
  • diarrheal form
  • paralytic form.

The sub-forms are characterized by different key symptoms and can, under certain circumstances, merge into one another. In individual cases, the respective form of poisoning can only occur with diffuse boundaries to the other three forms.

Sometimes only three forms of mussel poisoning are distinguished instead of the four mentioned. This classification relates primarily to the anatomical system in which the symptoms of poisoning occur. According to this scheme, the allergic and the gastrointestinal form are distinguished from the neurotoxic form. The triggering toxins usually get into the mussels via the water and the food chain. In oysters, however, endogenous toxins are produced during the spawning season. Putrefactive substances in mussels can also cause poisoning.


Mussel poisoning mainly occurs after eating mussels and scallops. Poisoning symptoms are also observed less frequently after the consumption of oysters. In the case of neurotoxic poisoning, the symptoms of poisoning are caused by neurotoxins. For example, dinoflagellates form saxitoxin in plankton. The mussels accumulate this substance in the meat during planction filtration. Red and diatoms, on the other hand, produce domino acids and are also part of the food chain of various mussels.

The diarrheal form is caused by okada acids. Brevetoxins also occur as toxins in mussels and can therefore also be the cause of mussel poisoning. Some shellfish poisoning is caused by the products of decay that build up in shellfish that are no longer fresh. These putrefying products mainly cause gastrointestinal problems in humans . Incidentally, it is a widespread misconception that toxins like the ones mentioned can be boiled out or washed off.

Symptoms, Ailments & Signs

The symptoms of mussel poisoning differ with the causative toxin and its dosage. In the gastro-intestinal form, the putrefactive products of the mussels cause gastrointestinal problems, the severity of which depends on the dose and the age of the mussels. Diarrhea and vomiting are the main symptoms. Chills can accompany it. Allergic mussel poisoning usually causes harmless skin rashes .

The paralytic form caused by neurotoxins is characterized by globus sensations in the throat, paraesthesia and paralysis . Movement disorders and speech disorders also occur. The body temperature of patients rises, sometimes life-threateningly, and anxiety and disturbances of consciousness occur. In the central nervous form, breathing difficulties are present. The paralytic form is the most severe form of mussel poisoning and can cause respiratory or cardiac arrest .

Diagnosis & course of disease

Doctors diagnose mytilism primarily through history. The local occurrence allows the doctor to assess the probability of the individual forms of mussel poisoning. The clinical picture is relatively typical for fish and mussel poisoning. However, the differential diagnosis between the individual forms of poisoning is often associated with problems in individual cases.

The detection of certain toxins in the mussel meat is considered to confirm the diagnosis, but can only rarely be provided. The course of the poisoning depends strongly on the specific toxin and its severity. Life-threatening courses can occur, especially in the paralytic form. The prognosis is generally more favorable for the other forms.


Serious physical problems can result from mussel poisoning. Side effects such as diarrhea and vomiting or chills usually occur, which if left untreated can lead to dehydration and circulatory problems. In severe cases, mussel poisoning can cause speech and movement disorders. Sometimes the body temperature rises life-threateningly and it comes to anxiety and disturbances of consciousness.

The central nervous form can cause breathing difficulties, while the paralytic form can lead to respiratory and cardiac arrest. Rarely, a toxi infection can occur, which can lead to blood poisoning. People who are already physically weak or overworked are particularly at risk of such complications. For example, pregnant women, the elderly, small children, patients with a weakened immune system and other risk groups.

In the treatment of mussel poisoning, the prescribed drugs can cause intolerance and allergic reactions. Many antibiotics cause gastrointestinal problems, skin rashes and physical discomfort. As part of the frequently prescribed ergotherapy, physical overload can occur or the already weakened immune system can be overburdened. As a rule, however, mussel poisoning can be cured without major complications if it is recognized and treated early.

When should you go to the doctor?

If the person concerned experiences severe discomfort, nausea or vomiting immediately after or during the consumption of mussels, a doctor should be consulted. A doctor is needed in the event of sweating, pale skin and a sharp drop in blood pressure. In acute cases, an emergency service must be alerted, as the person concerned must be treated immediately in intensive care. Otherwise there is a risk of premature death in the event of mussel poisoning.

Severe diarrhea, stomach pain and cramps are other signs of an irregularity. If you experience an increase in body temperature, a feeling of internal heat or dizziness, consult a doctor. Sudden changes in the appearance of the skin, itching or abnormal sensations on the skin must be examined and treated. There is also a need for action in the event of paralysis or breathing difficulties. If there is a failure of breathing or a sudden loss of consciousness, an emergency doctor must also be called. In order to ensure the survival of the person concerned until his arrival, first aid measures must be taken by those present at the same time.

If the symptoms mentioned occur after or during a visit to a restaurant, a doctor’s visit is also necessary. In some cases, chefs use mussels to enhance or flavor a prepared meal, so that leftovers or bits of mussel meat are incorporated into a menu without the knowledge of the person concerned.

Treatment & Therapy

Mytilism cannot be treated causally, only symptomatically. For example , if there is shortness of breath , supplying the patient with oxygen may be indicated. Symptoms of the gastrointestinal tract can lead to dehydration . If necessary, this dehydration is corrected by giving fluids intravenously.

In order to drain the toxins from the body as quickly as possible, the water balance should be kept relatively high. This stimulates the elimination of toxins in the urine. If there are dermatological symptoms, the itching is relieved with ointments and poultices. Anxiety can be alleviated by the targeted administration of tranquilizers.

However, the condition of the cardiovascular system plays a decisive role, since heart failure can occur if it is not taken into account. Pumping out the stomach is usually no longer effective when the first symptoms appear, as the toxins are already absorbed into the blood within two to five hours. If paralysis has set in that does not resolve itself within the next few days, physiotherapeutic treatment to regain mobility may be indicated.

Occupational therapy can also make sense in this context. If there are persistent speech disorders, a speech therapist is usually consulted .

Outlook & Forecast

The prognosis for mussel poisoning depends on the exact toxin, the site of action and the dose. Many mussel poisonings are considered harmless. Poisoning that only affects the digestive tract is usually well tolerated. The only danger here is dehydration as a result of diarrhea. Permanent damage is not to be feared with this form of mytilism. This form of poisoning is mostly caused by okadaic acid.

With other forms of mussel poisoning, the prognosis is much worse. Domoic acid, ciguatoxin and saxitoxin are much more dangerous and can lead to respiratory or circulatory problems. It is possible for those affected to survive the poisoning despite serious symptoms. In other cases, the condition can become life-threatening, especially when high doses of the poison are ingested. In these cases, poisoned people must be treated as soon as possible. The death rate increases with increasing duration of poisoning without help and treatment.

A treated and survived mussel poisoning leaves no consequential damage. A full recovery from temporary physical weakness is usually the result. It should be remembered that mussel poisoning has nothing to do with the immune system and can occur again and again.


Mussel poisoning can be prevented. For example, mussels from impure waters should not be eaten. Basically, mussels should always be soaked in pure water before consumption so that they detoxify their toxins. In the summer months, it is advisable to generally avoid mussels, as many algae form in the warm season and mussels come into contact with their toxins more often in summer.


Since mussel poisoning is associated with a serious course of infection in the gastrointestinal tract, the patient only fully recovers after a few weeks. During the follow-up care, the patient should consistently pay attention to the correct selection of foods that are gentle on the stomach and intestines. During this time, food should also be prepared very gently and in a way that relieves the stomach and intestines.

Foods with an increased risk of germs, such as raw meat, raw egg products or fish, should be avoided. Gastrointestinal sanitation is advisable as part of the follow-up treatment. This is usually done with the help of preparations with living lactic acid bacteria, which are taken over a few weeks to stabilize and build up a healthy intestinal flora. Since the immune system and the gastrointestinal tract have been weakened and impaired, the organism is very susceptible to further infections and diseases caused by bacteria and germs.

The follow-up examinations by the doctor treating you must therefore be carried out very promptly, if necessary as a result of renewed gastrointestinal complaints. If diarrhea occurs again, the patient’s stool should be examined in a laboratory. Through follow-up examinations, the doctor will diagnose whether gastritis may have developed from the mussel poisoning. This would then have to be treated medically and medicinally.

You can do that yourself

There is no antidote to mussel poisoning. Self-help measures must therefore focus on prevention and treatment of the individual symptoms. If mussels cause gastrointestinal problems, this is usually because the food was not really fresh when it was eaten and putrefactive substances have already formed. If you prepare mussels yourself, you should always buy them fresh and use them on the same day. However, certain symptoms of poisoning result from neurotoxins that the mussels accumulate in their flesh. There is little room for preventive measures here. However, this phenomenon occurs less frequently with oysters than with other types of mussels. So if you don’t want to do without completely, you can reduce the risk of neurotoxic poisoning by

Nausea, diarrhea and vomiting are usually rather harmless symptoms of mussel poisoning. In mild cases, these side effects can also be treated with over-the-counter medication from the pharmacy . In addition, the person affected should allow themselves rest and make sure that they compensate for the loss of fluids, which is often associated with diarrhea. In addition to water, unsweetened tea or vegetable broth should be drunk. Since the electrolyte balance is often disturbed, nibbling on savory snacks can be helpful.

If paralysis, speech disorders, anxiety, impaired consciousness or breathing difficulties occur, a doctor must be consulted immediately. In this case, the patient’s life is in danger, since severe forms of shellfish poisoning can lead to respiratory or cardiac arrest.

Lisa Newlon
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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.