Naphthalene Poisoning

Naphthalene poisoning occurs primarily as a result of accidental mothball ingestion, causing symptoms such as nausea, vomiting, hematuria and severe respiratory, neurologic and hepatic effects. Patient history is vital during workup, while detection of methemoglobinemia and cyanosis requires prompt therapy consisting of methylene blue and exchange transfusion.


The clinical presentation of naphthalene poisoning primarily includes gastrointestinal complaints such as nausea, vomiting, diarrhea and abdominal pain, but other systems are affected as well [2]. Hematuria, acute respiratory distress (ARDS), altered consciousness, convulsions, jaundice, hepatomegaly and hemolytic anemia are notable symptoms of severe poisoning [3].


A carefully obtained patient history is vital during workup, as key information regarding the source of symptoms and the mode of poisoning can be obtained. Assessment of hepatic and renal function, urinalysis, and arterial blood gasses are necessary for determining the state of tissue oxygenation and the degree of organ damage.


As soon as a presumptive diagnosis is made, immediate administration of methylene blue is indicated. Methylene blue is able to revert the process of hemoglobin conversion to methemoglobin due to its electron-absorbing properties and it effectively scavenges the remaining free radicals [3]. In addition, exchange transfusion is recommended in more severe cases like the G6PD deficiency patients [3]. Supportive measures consisting of adequate airway management as well as the use of fluids and inotropic drugs to sustain normal pressure are vital in preserving the cardiovascular and pulmonary systems [3].


Early recognition of the condition and prompt initiation of therapy carries a good prognosis, but various complications may arise, most notable being profound cyanosis induced by methemoglobinemia [2]. Additionally, severe hemolysis may occur in patients suffering from glucose-6-phosphate dehydrogenase (G6PD) deficiency, in whom a very low tolerance to oxidative stress exists [5], and renal failure may ensue in these patients without removal of naphthalene from the circulation.


Naphthalene is an aromatic hydrocarbon that is insoluble in water and poisoning almost universally occurs due to accidental ingestion of mothballs that are used as insect repellents [4]. An additional mode may be intentional ingestion, as suicide attempts with mothballs have been reported [1] [4].


Exact rates of poisoning are unknown, but in the United States, approximately 1500 cases were reported in 2007 and 2008 [2]. The majority of patients are children.

Sex distribution
Age distribution


Once naphthalene is introduced into the human body, most likely through accidental ingestion, it is degraded in the liver by cytochrome P450 enzymes [2]. However, an abundance of free oxygen radicals is released during this process, leading to marked oxidative stress that causes lipid peroxidation, DNA damage and formation of methemoglobin [2].


Because of the fact that naphthalene poisoning is accidental in most cases, avoiding the use of mothballs in households or placing them out of children's reach can be an effective preventive measure.


Naphthalene poisoning is very rarely encountered in clinical practice and the majority of cases are children who accidentally ingest mothballs that contain this aromatic hydrocarbon [1]. After ingestion naphthalene causes marked oxidative stress resulting in methemoglobinemia and hemolysis of red blood cells [2]. Methemoglobinemia is the most significant manifestation of toxicity by naphthalene. The other symptoms may include a headache, vomiting, diarrhea, abdominal pain and altered mental status [3]. The diagnosis mandates a thorough patient history that can reveal the source of symptoms, whereas a complete laboratory workup is necessary to define the extent of organ damage. Treatment mandates prompt administration of methylene blue, which is able to reverse the effects of free radical damage, but also exchange transfusion, in the attempt to remove naphthalene from the circulation [1].

Patient Information

Naphthalene is an aromatic hydrocarbon that is ubiquitously present in the air in very low concentrations, but its most frequent household use is in mothballs as an insect repellent. Consequently, naphthalene poisoning almost universally occurs after accidental ingestion of mothballs by children. Once this substance enters the body, it causes damage to cell membranes and releases numerous free radical that are responsible for tissue destruction. The most important consequence of poisoning, however, is the conversion of hemoglobin to methemoglobin, which has reduced ability to bind to oxygen. Within several hours or few days, symptoms like nausea, vomiting, diarrhea, abdominal pain, together with cyanosis, darkening of urine due to the presence of hemoglobin and confusion, altered consciousness, and even lethargy may occur. The diagnosis can be made by obtaining a meticulous patient history that will reveal the source of poisoning. Treatment mandates the use of methylene blue, which effectively reduces the harmful effects of naphthalene. Special care is needed for individuals suffering from glucose-6-phosphate dehydrogenase (G6PD) deficiency, as they are more susceptible to free radical damage. In this subgroup, a procedure known as exchange transfusion is necessary to perform.


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  3. Kundra TS, Bhutatani V, Gupta R, Kaur P. Naphthalene Poisoning following Ingestion of Mothballs: A Case Report. Journal of Clinical and Diagnostic Research : JCDR. 2015;9(8):UD01-UD02.
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