When you find bed bugs, sleeping with the lights on is one of the first things people try. It feels logical, since they hide during the day and come out in the dark. The research says bed bugs do prefer darkness, but light is not what tells them when to feed. Here's what studies show about bed bugs and light, why a lit bedroom doesn't protect you, and how to use light to find them instead.
Yes, bed bugs will come out with the lights on if they're hungry and you're there. In lab studies they're much more active in the dark, but that's only their default when no one is around. What draws them out is a person: the carbon dioxide in your breath and the warmth of your body.
Sleeping with the lights on won't keep them away. University of Kentucky entomologists note that hungry bed bugs "may also feed during the day, especially if this is when the occupant normally sleeps." A lamp costs you sleep without stopping the bites. Use the light to catch them instead.
What Research Shows About Bed Bugs and Light
| Question | What the research found |
|---|---|
| Are they more active in the dark? | Yes, by default. In a University of Kentucky study, adults and nymphs with no host nearby were "much more active in the dark than in the light," starting soon after lights-off (Romero, Potter and Haynes, 2010) |
| Can they change their schedule? | Yes. When researchers reversed the light and dark periods, the bugs shifted their activity to match within four cycles |
| Does hunger matter? | Yes. Recently starved adults moved around more than recently fed ones |
| What draws them to you? | Host cues. In a University of California study, human breath triggered long-range host-seeking, while bugs without it moved only in short, local bursts (Suchy and Lewis, 2011) |
| Do they feed in daylight? | They can. Hungry bed bugs "may also feed during the day, especially if this is when the occupant normally sleeps" (University of Kentucky) |
| Do they avoid light colors? | They prefer to hide in black and red spots over white, yellow, green or blue ones (Singh, Wang and Cooper, 2015; McNeill et al., 2016) |
So bed bugs aren't repelled by light the way a cockroach scatters when you flip a switch. They're nocturnal by habit, and they keep hidden because the dark protects them while you're awake and moving. Once you're lying still, breathing out carbon dioxide and giving off heat, a hungry bug has a reason to come out regardless of the lamp.
Will Sleeping With the Lights On Keep Bed Bugs Away?
No. It won't stop a hungry bed bug, and you'll sleep worse. The research above explains why: a bug that can shift its whole schedule within a few days isn't going to starve because a lamp is on.
People who have tried it say the same. In Reddit's bed bug forums (via Google search excerpts), one person wrote that they had been "sleeping with the lights on because I'm so afraid" for two months and were still being bitten every day. Asked whether sleeping with the lights on keeps them away, one reply was blunt: "Nope. It's a good way to catch them in the act though." That person found out they had bed bugs exactly that way, after falling asleep with the lights on.
There's also footage. In a BBC Bang Goes the Theory segment on YouTube (about 6 million views), entomologist Dr. James Logan puts a bed bug on his arm in his lab, and after a short wander it starts feeding on camera, under the lights of a TV shoot.
Why You Might See Bed Bugs During the Day
- You sleep during the day. Night-shift workers get bitten in daylight because the bugs follow the sleeper, not the clock.
- They're hungry. Starved bugs are more active and more likely to come out at odd times.
- Someone is resting nearby. A person napping on a couch or sitting still in a recliner gives off the same cues as a sleeper.
- There are a lot of them. In a larger infestation you're simply more likely to see bugs on walls, sheets and furniture at any hour.
Seeing one in daylight doesn't automatically mean a huge infestation, but it does mean you should check for bites and other signs and get an inspection.
How to Use Light to Find Bed Bugs
Light won't keep bed bugs away, but it's the best tool you have for finding them.
- Check during the night or just before you'd normally wake up. Switch on a bright flashlight and look along the mattress seams, the headboard and the sheets near your pillow.
- Inspect hiding spots in daylight. Use a flashlight along seams, piping, tags and box spring corners. Look for live bugs, pale eggs, shed skins and dark ink-like spots.
- Catch the ones that wander. Put interceptor cups under the bed and couch legs. Bugs walking to or from you fall in and can't climb out, light or dark.
- Use a dark trap color. Bed bugs prefer black and red hiding spots, and in one study a trap with a black or red outside caught more bugs than a white one.
- Bag a sample. Trap anything you catch on clear tape so a pest professional can confirm it's a bed bug.
Other Things That Don't Keep Bed Bugs Away
- Sleeping in another room. The bugs follow you and can spread to the new room.
- Leaving the home empty. The University of Kentucky warns that bed bugs in empty apartments often move to nearby units or go quiet until someone returns.
- Bug bombs. The University of Kentucky says foggers don't work on bed bugs and are a fire risk.
What does work is a planned treatment with follow-up visits. See how long bed bug treatment takes for a realistic timeline, and our bed bug control service for help in South Carolina, North Carolina and Virginia.
En español: ¿Las chinches salen con la luz prendida?
Sí. Las chinches de cama prefieren la oscuridad, pero la luz no las detiene si tienen hambre y hay una persona cerca. Lo que las atrae es el dióxido de carbono de la respiración y el calor del cuerpo. Según la Universidad de Kentucky, las chinches hambrientas también se alimentan de día, sobre todo si la persona duerme durante el día.
Dormir con la luz encendida no las aleja. Solo le quita el sueño. Es mejor usar la luz para encontrarlas: revise con una linterna las costuras del colchón, la cabecera y las sábanas cerca de la almohada, y ponga trampas debajo de las patas de la cama. Si encuentra chinches, llame a un profesional.
Key Takeaways
- Bed bugs prefer the dark when no one is around, but light doesn't repel them.
- They respond to you: your breath and body heat draw them out, lights on or off.
- They adjust their schedule, shifting to a reversed day and night within a few days in lab tests, and feeding by day when people sleep by day.
- Sleeping with the lights on doesn't work. Use the light to catch them instead.
- Check with a flashlight before dawn and use interceptor cups under bed and couch legs.
Frequently Asked Questions
Yes, if they're hungry and someone is there. Bed bugs are much more active in the dark when no host is around, but they're drawn out by the carbon dioxide in your breath and your body heat. The University of Kentucky notes hungry bed bugs may feed during the day, especially when that's when the person sleeps.
No. Leaving a light on doesn't stop a hungry bed bug from feeding, and lab studies show bed bugs can shift their activity to a reversed light schedule within a few days. People who try it report still getting bitten. Use the light to inspect for them instead.
Not in the sense of being repelled by it. They're nocturnal by habit and hide in dark cracks during the day, but light alone doesn't keep them from coming out to feed when a person is sleeping nearby.
They can be. They normally hide during the day close to where people sleep, but hungry bed bugs will feed in daylight, especially if someone sleeps during the day, such as a night-shift worker, or is resting still on a couch.
No. They aren't drawn to lights the way moths are. What attracts them is a host: carbon dioxide, body heat and skin odors. They also prefer dark, black or red hiding spots over light-colored ones.
Mostly. In a University of Kentucky study, bed bugs with no host nearby were much more active in the dark, starting soon after lights-off. But they adjust to when people sleep, so they aren't strictly nocturnal.
No. The University of Kentucky says bed bugs don't fly or jump like fleas, but they crawl quickly over floors, walls and ceilings. That's why interceptor cups under bed legs can catch them.
During the night or just before you'd normally wake up, when hungry bugs are most likely to be out. Use a bright flashlight on mattress seams, the headboard and the sheets near your pillow. In daylight, check seams and cracks where they hide.
Sí. Las chinches prefieren la oscuridad, pero si tienen hambre y hay una persona cerca, salen aunque la luz esté encendida. Las atrae el dióxido de carbono de la respiración y el calor del cuerpo. Dormir con la luz prendida no las aleja.
Sources: A. Romero, M. F. Potter and K. F. Haynes, "Circadian rhythm of spontaneous locomotor activity in the bed bug, Cimex lectularius L.", Journal of Insect Physiology (2010); J. T. Suchy and V. R. Lewis, "Host-Seeking Behavior in the Bed Bug, Cimex lectularius", Insects 2:22 (2011); N. Singh, C. Wang and R. Cooper, "Role of vision and mechanoreception in bed bug, Cimex lectularius L. behavior", PLoS One (2015); C. A. McNeill et al., "Behavioral Responses of Nymph and Adult Cimex lectularius to Colored Harborages", Journal of Medical Entomology (2016); M. F. Potter, "Bed Bugs", University of Kentucky Entomology ENTFACT-636; BBC, "A Bedbug's Bite - Up Close! - Bang Goes the Theory", YouTube; homeowner accounts from Reddit (via Google search excerpts).
Photo credits: CDC / Harvard University, Dr. Gary Alpert, Public domain; OH-BugMan, CC BY-SA 4.0, via Wikimedia Commons.