A nightlight is a small light fixture, often electrical, placed for comfort or convenience in dark areas or areas that may become dark at certain times, such as in an emergency. Small long-burning candles serving a similar function are referred to as tealights.
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People often use nightlights for the sense of security which having a light on provides, and for a solution against nyctophobia (fear of the dark). Besides their usefulness to children in the allaying of their fears, nightlights are also useful to the general public by showing the general layout of a room without turning on a major light, for avoiding tripping over stairs or obstacles, or to mark an emergency exit. Exit signs often use tritium in the form of a traser.
There are a wide variety of electrical nightlights. Most based on incandescent bulbs have a power usage of less than 10 watts; lights based on more efficient technologies, such as electroluminescence, neon lamps, or LEDs, use one watt or less. They sometimes have a light-sensitive component (such as a photoresistor) which activates them only when it is dark enough for them to be required or activate automatically in dark weather. Some include an integrated rechargeable battery so that the light will continue to function during power outages.
The U.S. Consumer Product Safety Commission reports its receives about 10 reports per year where nightlights close to flammable materials were cited as responsible for fires; they recommend the use of nightlight with bulbs cooler than the four or seven watt bulbs used in some products.[1]
A 2004 study tentatively suggested that strong light at night time may pose an increased risk of certain cancers.[2] This may be due to the disruption of the normal production of melatonin, which has shown the ability to protect the body against cancer development. However it also claimed that there is no evidence linking light at night specifically to childhood leukemia, the causes of which are not fully understood.
A University of Pennsylvania study indicated that sleeping with the light on or with a nightlight was associated with a greater incidence of nearsightedness in children.[3] A later study at The Ohio State University, however, contradicted the earlier conclusion.[4] Both studies were published in the journal Nature.
Another study has indicated that sleeping with the light on may protect the eyes of diabetics from retinopathy, a condition that can lead to blindness.[5] However, the initial study is still inconclusive.