Bed Bug Bites: How to Tell Them Apart From Other Bites

When should you see a doctor about bed bug bites?

Call 911 or your local emergency number right away if someone has trouble breathing, wheezing or shortness of breath, swelling anywhere on the face or in the mouth, throat tightness or trouble swallowing, feels weak or turns blue after a bite ^[6]. Those are signs of a whole-body allergic reaction. CDC says serious allergic reactions to bed bug bites are rare, but anaphylaxis can happen ^[1].

See a doctor or other healthcare provider in these situations:

• You think you are having an allergic reaction, such as enlarged bite marks or painful swelling at the bite. CDC tells people with these signs to speak with a healthcare provider ^[1].
• A bite looks infected. CDC describes an infected bite as red, warm to the touch, or with a red streak spreading out from it, and says to see a provider if symptoms get worse ^[7].
• You have a fever, or a rash that keeps spreading, or a bite that gets worse instead of better after a few days.
• The mark could be from a tick. A rash that grows larger over several days, sometimes shaped like a bull's-eye, can be the first sign of Lyme disease. It usually starts 3 to 30 days after a tick bite ^[8].

If a bite worries you, ask a doctor or pharmacist what to do for the itch instead of guessing. Scratching can break the skin, and scratched bites can lead to infections ^[4].

What do bed bug bites look like?

Bed bug bites usually look like mosquito or flea bites: a slightly swollen, red area that may itch and feel irritated ^[1]. The University of Kentucky describes the typical reaction as an itchy red welt ^[5]. Some people get larger itchy swellings ^[4].

A few details can point toward bed bugs, though none of them is proof:

• Where the marks are. Bites are common on the face, neck, arms, hands or any other skin that was exposed while you slept ^[1].
• The pattern. Marks may be random or in a straight line ^[1].
• When they happened. Bed bugs mostly feed at night while people sleep. A feeding takes about 3 to 10 minutes and is painless, so people rarely feel it ^[5].

The reaction also depends on the person. About 30 percent of people do not react even when bitten repeatedly, and older adults are less likely to react ^[5]. That means one person in a shared bed can have itchy welts while the other has none, even though both were bitten.

How long do bed bug bites take to show up?

Most people do not notice bed bug bites right away. Marks usually appear one to several days after the bite and may take as long as 14 days to develop in some people ^[1]. The University of Kentucky notes that the reaction can be delayed by days or even weeks ^[5].

That delay is one reason bed bugs are so easy to miss. By the time welts appear, you may have slept in a hotel, a friend's guest room and your own bed, and it is hard to know where the bites happened. Other common bites follow a faster clock:

• Mosquito bites often form a puffy, reddish bump within a few minutes, then a hard, itchy bump a day or so later ^[7].
• Chigger bites usually start to itch about 3 to 6 hours after the bite, with the rash developing over roughly 10 to 16 hours ^[9].

How can you tell bed bug bites from other bites?

You often cannot tell them apart by looking. EPA says bed bug bites can look like bites from mosquitoes or chiggers, and like rashes such as eczema, fungal infections or hives ^[2]. The University of Kentucky adds that bed bug welts are often blamed on mosquitoes ^[5]. The table compares the clues that sources do describe.

Cause	Typical look	Timing	Where and when	Best clue
Bed bugs	Red, slightly swollen, itchy area; random or in a line	1 to several days, up to 14	Skin exposed during sleep, at night	Bugs, dark spots or shed skins in the bed
Mosquitoes	Puffy reddish bump, then a hard itchy bump	Minutes, then a day or so	Outdoors or open windows, any exposed skin	You saw or heard mosquitoes
Fleas	Small red spot with a red halo, usually little swelling	Itch can last up to 5 days	Homes with cats or dogs	Fleas on pets or in pet bedding
Chiggers	Itchy red bumps	Itch in 3 to 6 hours	Where clothing is tight: sock line, waistline	Recent walk in tall grass or brush
Carpet beetle larvae	Itchy rash that feels like bites, but no bite happened	Builds with repeated contact	Contact with larvae in fabrics or bedding	Fuzzy larvae or cast skins in closets and rugs

Sources for the table: CDC on bed bugs and mosquitoes; UC IPM on fleas ^[10]; NC State on chiggers; Penn State on carpet beetle larvae, whose hairs can cause an intense itch and rash in people who are sensitized after long exposure ^[11].

The last row matters more than it looks. Carpet beetles do not bite, yet their larvae can leave people sure that something is biting them at night. If you have carpet beetles in a closet or rug and no sign of bed bugs, that rash may have a different cause. Our pages on chiggers and what a flea looks like can help you check the other suspects, and the bite identifier tool walks through the same questions step by step.

Can you be sure bed bugs caused your bites?

No. You cannot identify a bug from a bite with certainty, and neither can a photo of a bite. EPA calls bites "a poor indicator" of a bed bug infestation ^[2], and UC IPM says the only way to really confirm bed bugs is to find the bugs or their signs ^[4]. The best clue is always finding the bug itself.

Check the mattress seams, box spring, bed frame, headboard, nightstand and nearby cracks. CDC says bed bugs tend to live within 8 feet of where people sleep ^[1]. EPA lists the signs to look for ^[2]:

1. Rusty or reddish stains on sheets or the mattress, from crushed bugs
2. Dark spots about the size of a printed dot, which are droppings and can bleed into fabric like a marker
3. Eggs and eggshells about 1 mm long, and pale yellow skins that young bugs shed as they grow
4. Live bugs, often tucked into seams and folds

Use a flashlight and a magnifying glass, because the smallest stages are tiny. CDC says bed bugs range from 1 mm to 7 mm, roughly the size of Lincoln's head on a penny for the larger ones ^[1]. EPA puts adults at about 5 to 7 mm, the size of an apple seed ^[3]. See what a bed bug looks like for the full identification guide and our bedroom page for other pests that turn up near beds.

Do bed bug bites spread disease?

No. CDC says bed bugs are not known to spread diseases to people ^[1], and UC IPM says they have never been shown to transmit human disease ^[4].

That does not mean bites are harmless. CDC lists other effects: allergic reactions in some people, skin problems from scratching, and trouble sleeping or anxiety ^[1]. Losing sleep night after night is a real cost, and it is a fair reason to talk with a doctor even when the bites themselves look mild.

The bites also tell you something about the home. If you confirm bed bugs, the bites will keep coming until the bugs are gone, so the next step is control, not waiting. Our guide on how to get rid of bed bugs covers heat, encasements, interceptor cups and when to call a licensed pest professional. For quick facts on the insect itself, see the bed bug profile.