How Bedbugs Are Diagnosed

Updated on July 10, 2021

Medically reviewed by

Bedbugs are diagnosed in two ways. The first is the appearance of bites on your body. However, these are very similar to other insect bites and can appear days after being bitten. Finding the signs of bedbugs in your sleeping environment is more conclusive evidence that there is an infestation. You will usually do your own self-diagnosis, but you might see a healthcare provider due to unexplained bite marks or a skin infection after scratching. Learn how to determine whether you have been bitten by bedbugs.

bedbug bites diagnosis — © Verywell, 2018

Self-Checks

It is difficult to tell bedbug bites from those of mosquitoes, fleas, or other insects. You likely won't feel bedbugs biting as they inject an anesthetic and anticoagulant when they bite. You may develop bite marks one to 14 days after being bitten. As with mosquitoes, their saliva can provoke an allergic reaction at the site of the bite. Some people have no reaction, others have a mild one, while some can have significant swelling.

A typical reaction the first time you are bitten is a red, itchy bump, and you may see a central blood dot. When you have repeated bites, your body may react in different ways and the bites can form wheals or blisters.

The bite marks may be in a straight line, cluster, or a random pattern. One classic pattern is three bites in a line—breakfast, lunch, and dinner. Bedbugs are not picky eaters when it comes to location—any exposed skin will do—but they won't necessarily go farther than they have to. Bites typically occur on the face, hands, and feet.

Close up around ankle of woman with rash cause from bed bugs bite — An ankle with a rash from bed bug bites. Hemjaa / Getty Images

Environmental Checks

The only way to know for sure if your symptoms are, in fact, a result of bedbugs, is to find the bed bug infestation in your room or furniture.

You can check bedding, mattresses, furniture, and crevices in walls for bedbug infestation. Do your inspection just before dawn, which is when they are the most active. The bugs will be larger and slower after feeding. Bedbugs will quickly flee from light, so live bugs are best located in the folds and seams of mattresses and sheets. Bedbugs are about the size of an apple seed, about 1/4 inch long. They change from light brown to purple-red after feeding. You may also see their eggs, which are about the same size as the adults. The eggs will often be in seams, cracks, or crevices.

You are more likely to find their molted exoskeletons and dark specks of their feces. Also look for rust-colored blood spots on bedding and mattresses, which can come from the blood in their feces or from having crushed a bedbug who was feeding. A room with a heavy bedbug infestation might have a sweet, musty odor.

Differential Diagnoses

Most of the time you won't go to a healthcare provider for bedbug bites. However, the bites can mimic other rashes or you might develop a skin infection from scratching, and those factors may send you to the healthcare provider.

Be prepared with a timeline of your symptoms. You should note any travel you have done, any new furniture, bedding, or mattresses, and a list of your medications and supplements. Bring photos of any suspicious specks found on your bedding or furniture.

Your healthcare provider will perform a physical exam and take your medical history. This is usually enough to make the diagnosis or rule out other causes.

Some diagnoses your healthcare provider will consider due to your bite reactions include:

Mosquito, flea, chigger, tick, or spider bites: These can look very similar in appearance to bedbug bites and it may not be possible for a healthcare provider to tell the difference.
Scabies: This is a parasitic mite that is spread by skin-to-skin contact. It lays eggs under the skin and an itchy rash develops when the larva hatch.
Lice: Body lice and head lice can lead to scratching, with inflamed or infected scratch marks.
Antibiotic reaction
Eczema
Fungal skin infection
Hives
Food allergy
Chickenpox

Environmental Diagnosis of Bedbug Infestation

If you are unsure whether what you find are traces of bedbugs, the National Pesticide Information Center lets you search for local resources that can help with identification of photos or samples you collect. You may want to enlist a professional pest control expert to determine whether or not you have bedbugs in your home and what rooms might be infested.

Frequently Asked Questions

What do bedbug bites look like?

Bedbug bites look like small red lesions. They typically start off as red bumps that may develop into itchy blisters. The bites are often formed in a line or clustered in a small group. If the bites are very close together, they may form a larger rash.
How can I tell if I have bedbug bites or another type of bug bite?

Because bedbug bites look very similar to other insect bites or skin rashes, it can be difficult to narrow down a diagnosis. The best way to confirm you have bedbugs is to look for evidence of the bugs themselves—search carefully within your bedding, in the seams of your mattress, and in the crevices between the carpet and the wall.
Where do bedbugs typically bite?

Bedbug bites are most commonly found on the face, neck, hands, and arms, but they can also appear anywhere else on the body.
Can bedbugs bite pets?

Yes, bedbugs may feast on pets and other animals, though they prefer human blood.
How can I heal a bedbug bite?

Bedbug bites usually go away on their own, similar to a mosquito bite. But if the itching gets to be too intense, calamine lotion or an over-the-counter topical cream containing cortisone or diphenhydramine can help educe scratching and thereby prevent a secondary infection.

How to Get Rid of Bedbugs and Their Bites