Some metals are needed by the body for various body processes such as iron, cobalt, calcium, magnesium, sodium, potassium, copper manganese, zinc and many others. However, mercury is not one of them.

When mercury is accidentally ingested, it reacts with selenium, an important element that reverses oxidative damage in the endocrine system and central nervous system. Selenium is also responsible for the restoration of vitamin C and vitamin E and other antioxidants to their reduced forms, which allows these antioxidants to reduce free radicals and oxidative stress in the body. When mercury is ingested and reacts with selenium, it greatly affects and impairs the functioning of selenium in reducing oxidative stress, thereby leading to dysfunction in the brain cells that may eventually lead to neuronal cell death. The ingestion of mercury in small doses may produce short-term results, but the continuous ingestion of such may lead to more permanent brain damage.

Aside from this, accidental ingestion of mercury in large amounts may lead to mercury poisoning or mercurialism and hydrargyria.  Mercury is one of the most harmful metals that can be ingested by humans because it causes various side-effects including:

• Peripheral neuropathy
Peripheral neuropathy is a condition involving the presence of paresthesia or abnormal sensations in the arms and legs such as numbness, pins and needles and pain.
• Skin discoloration
Mercury poisoning may also lead to abnormal pinkish color of the fingertips, toes and cheeks.
• Shedding of the skin
People suffering from mercury poisoning may also experience shedding of the skin as a result of oxidative stress in the cells leading to a fast cell death of the skin cells.
• Hypertension
Ingestion of mercury may also lead to high blood pressure due to increased levels of catecholamine or epinephrine.
• Tachycardia
An abnormal and fast heart rate also develops because of the continued fight and flight response as a result of increased epinephrine levels.
• Kidney dysfunction
Elevated mercury levels may damage the cells in the kidneys leading to Fanconi syndrome in children.
• Cognitive impairment
The oxidative stress effect in the brain cells may also slow the cognitive functioning of people leading to memory impairment, emotional liability, and insomnia.

Mercury is also toxic to pregnant women and may cause serious birth defect in the fetus. It may also lead to inhibition of the formation of myelin sheath in children leading to reduced neuronal functioning. In men, mercury ingestion may lead to a low sperm count and bronchiectasis or the formation of nodules in the bronchus.

The main reason for ingesting mercury is the consumption of fatty fish such as dolphins, whale, sharks, and other big fish. These fish contain high amounts mercury because of their consumption of other small and dead fish. Mercury contamination in humans may also be due to inhalation of contaminated air in factories using mercury as well as exposure of mercury in dental amalgams. The most serious source of high doses of mercury is from exposure to mercury emitting coal plants among workers. To prevent the harmful effects of mercury, make sure to avoid mercury exposure from the above sources.