health Apr 15, 2022

Erethism is a neurological disorder which affects the whole central nervous system, and is characterized by emotional, mental, and behavioral changes such as irritability, low self-confidence, depression, apathy, shyness and timidity among other symptoms.
The term Erethism means abnormal irritability or responsiveness to stimulation and a state of abnormal mental excitement or irritation.
This disorder is caused by chronic mercury poisoning and is also known as Erethism or Erethism mercurialis or mad hatter's disease or Mad hatter syndrome and it is caused by mercury poisoning that can occur due to the mercury vapor inhalation, mercury ingestion, mercury injection, and absorption of mercury through the skin.
Erethism produces harmful effects on the nervous, digestive and immune systems, lungs, kidneys, skin, thyroid, breasts, muscles, adrenal glands, testes and prostate.


According to WHO, exposure to Inorganic and Organic mercury causes Erethism.

Inorganic exposure may be

  • through the job or workplaces such as in factories or workshops that produce batteries, lamps, or light bulbs, measuring devices, such as thermometers, and barometers,
  • through contact with mercury in “silver “dental fillings, or cosmetics, broken fever thermometers or blood pressure monitors, mining for gold, household gold extraction, CFL bulb breakage,
  • exposure to toxic air in industrialized communities.

Organic exposure may be through eating certain types of mercury-containing fish and eating too much fish

  • All types of fish contain some amount of mercury. So, too much consumption of fish may cause erethism.
  • Volcanic activity causes the release of mercury and it enters the water, where it becomes methylmercury. It contaminates fish and eating such contaminated fish results in mercury poisoning.

Risk Groups

  • Individuals suffering from diseases of the liver, kidneys, nerves, and lungs
  • Individuals with insufficiency of zinc, glutathione, antioxidants, or selenium in diet
  • Individuals who are malnourished
  • Individuals with dental amalgams
  • Dose and duration to which persons are exposed
  • Dietary patterns of fish and seafood consumption


General symptoms of Erethism may be physical problems such as decrease in physical strength, headache, general pain, anxiety, depression, irritability, memory problems, numbness, pathologic shyness, tremors and high blood pressure, an increased risk of heart attacks, higher “bad” LDL cholesterol and an irregular heartbeat.
Symptoms of Erethism may also depend on degree of exposure, the kind of mercury and duration.
Depending on the degree of exposure to mercury poisoning, symptoms may be categorized as early and late.

Early symptoms of mercury poisoning are
A rash, skin itchiness, a wet cough, a metallic taste in the mouth, sores or inflammation in the mouth, stomach pain, vomiting, diarrhea, dehydration, muscle pain, sleep disturbances.
Later symptoms of mercury poisoning are
Anxiety, memory loss, trouble thinking or concentrating, irritability and a lack of patience, shyness and the desire to avoid people, changes in movement, which may be coarse or jerky, a tremor that begins in the hands and affects the face and head and insomnia.
Depending on the kind of mercury, mercury poisoning symptoms may be categorized as
Inorganic and organic

Symptoms of Inorganic mercury exposure are
Inorganic mercurous and mercuric compounds do not affect the central nervous system (CNS); but they affect gastrointestinal tract, immune system, and kidneys. Symptoms are abdominal pain, vomiting, diarrhea, dehydration and acute tubular necrosis.
Symptoms of organic mercury exposure are
Central Nervous System abnormalities like anxiety, irritability, mania, sleep disturbance, depression, cognitive deficits, visual disturbance, hearing loss, paresthesia, and tremor.

Depending on the duration of the exposure to mercury poisoning, symptoms may be categorized as Acute and Chronic

Acute exposures do not generally affect the CNS but cause respiratory distress and dyspnea (shortness of breath).

Chronic exposures cause loosening of teeth, tremors, delusions, memory loss, anxiety, abnormal gait, personality change, depression, irritability, nervousness, delirium, insomnia, suicidal tendencies, psychosis and cognition problems.
In addition to causing CNS abnormalities inhalation of elemental mercury can also cause pneumonitis, and pulmonary fibrosis.

Symptoms of mercury poisoning in Adults are
Adults may have vision changes, hearing and speech difficulties, lack of coordination, muscle weakness, nerve loss in hands and face, trouble walking

Symptoms of mercury poisoning in children and infants are
Infants may have delay in cognition, fine motor skills, speech and language development, and visual-spatial awareness.
Children exposed to mercury may suffer from pink disease (acrodynia), fever, generalized rash, splenomegaly, irritability, and poor muscle tone

If the poisoning is slight, symptoms of mercury poisoning (Erethism) degenerate and disappear as soon as exposure has ceased.


  • Erethism can be diagnosed with a physical examination
  • Blood or urine mercury test is used to measure levels in the body.
  • Toenail mercury analysis helps to diagnose erethism in people who consumed fish and shellfish
  • mass spectroscopy helps to measure mercury concentration in brain
  • Blood and scalp hair are the primary indicators used to assess erethism
    Blood levels are useful for more acute exposures and hair mercury levels are useful for long-term exposures
  • neuroimaging studies such as Radiography, MRI, Single-photon emission computed tomography (SPECT) and electrophysiological testing are conducted for selected cases


The best and traditional treatment is to avoid exposure to mercury poisoning.
The mercury concentration in whole blood is usually lower than 10 μg/L, but the value of 20 μg/L or below is considered normal.

  • If mercury levels are high, chelation therapy is used. It involves giving a medication (the chelator) that goes into the body and grabs the metal and carries the metal out of the body, usually into the urine. Thus, the therapy helps the body to dispose of them.
  • Activated charcoal can be used for gastrointestinal decontamination as it binds inorganic and organic mercury compounds to some extent.
  • In severe cases of toxicity, Hemodialysis is used when renal function has declined.
  • If patients are in unstable condition, they should be admitted to an intensive care unit (ICU) and carefully monitored.

Mercury poisoning can be reversible, if a person receives treatment in time.
If a person does not receive medical care, the poisoning can be fatal.

Precautions and prevention

  • Managing household spills of mercury such as from CFL bulb breakage
  • Avoiding activities with known mercury exposure risk, such as home gold extraction
  • Washing hands immediately if exposed to other forms of mercury.
  • Eating larger types of fish on an occasional basis.
  • Avoiding fish containing high levels of mercury
  • Taking a blood or urine mercury test before conceiving
  • fish and seafood serving guidelines of Food and Drug Administration (FDA) should be followed for children
  • Pregnant ladies should avoid fish containing high levels of mercury

Diet and guidance

  • Mercury poisoning is largely linked to eating seafood, mainly fish. All types of fish contain some amount of mercury.
  • Larger types of fish can have higher amounts of mercury because they prey on other fish that have mercury. Larger and longer-lived fish like shark, swordfish, fresh tuna, marlin, king mackerel, and tilefish usually contain mercury in higher levels. Such fish consumption should be avoided.
  • Fish like Salmon, shrimp, cod, and sardines can be eaten in small amounts, at once or twice per week.
  • To get rid of mercury, cilantro, garlic, wild blueberries, lemon water, spirulina, chlorella, barley grass juice powder, green tea, tomatoes, probiotics have to be taken. These foods bind to the metals and remove them in the digestion process.
  • Persons who are exposed to mercury, should take foods high in vitamins and minerals as they have protective effects.


A. Sandhya

M.Sc Zoology

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