Benzocaine cream is used topically to block pain and discomfort for a wide range of conditions, from teething to hemorrhoids, and to prepare for some cosmetic and minor medical procedures, according to eMedicineHealth and the FDA. It works by blocking nerve signals in the affected area.
Benzocaine cream is used to ease the pain of sunburn, sore throat, ingrown toenails or other minor skin irritations. It is used to numb the skin inside the mouth, nose and throat, and in the vagina or rectum, according to Everydayhealth.com.
When too much is used, benzocaine can pass from the skin into the blood stream, where it can cause serious adverse reactions, such as irregular heartbeat and seizures, according to the FDA. It has been used to numb large areas of skin, such as on the legs, to prepare for cosmetic procedures like laser hair removal. In such circumstances it has been known to cause serious side effects that lead to death.
When used in the mouth or throat, benzocaine can cause a life-threatening condition called methemoglobinemia, in which the oxygen levels in the blood fall to dangerously low levels, according to Everydayhealth.com. The reaction can be caused by one use or by use over time. Headache, confusion, fatigue, a racing heartbeat, feeling faint, shortness of breath or a white, grey or blue color in the lips, skin or fingernails are possible symptoms of methemoglobinemia and are considered a medical emergency.