Unknown & Mysterious Bug Bites

-- What's biting me at night??? --


People often report that they are being bitten by something, often at night, but there is no sign of a bug. While there are a number of insects and mites that bite and leave a red, swollen and itchy bite mark or lesion, there are also many other causes of skin irritation that can be easily mistaken for bug bites. In many cases, therefore, what appears to be a bug bite may in fact be caused by something else. Below you'll find a list of insects and mites that do bite as well as some things that can be mistaken for bug bites.

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Jack DeAngelis, ext. entomologist (ret.) revised: 11/2018

What if you have bug bites but can't find a bug?

I am frequently asked to diagnosis the cause of bug bites that seem to appear for no obvious reason. There is no insect or mite to identify and the person has either a vague description of what may have bitten them or, ironically, an extremely detailed description.

Most people who contact me believe there are many insects and mites that bite us. In reality there are very few that actually bite people. Take a look at the list of insects and mites below that actually do bite people. If you can not clearly identify one of these as the cause of your bites then you should consider some of the other possibilities. In the descriptions below notice that the bites are all very similar (red, itchy bumps) making any diagnosis from examining the bite alone nearly impossible.

bug bites
"Bug bites" on wrist and arm.

Bed bugs

Bed bugs cause large, red, splotchy, itchy, mosquito-like bites. Bedding and furniture can be infested and bed bug bites generally occur at night. Bed bug infestations are fairly easy to detect because the bugs themselves are relatively large and feeding results in stains on bedding and possibly a distinctive room smell, see this article for details.

bed bug
bed bug; all stages look similar

Mites that do bite people

There is a small number of mites that bite people resulting in itchy skin lesions. A very few also pose some health risk by transmitting disease like ticks or developing persistent skin conditions like scabies. The articles below should help you identify and treat the mites that bite people.

    Bird/nest/rodent mites - These mites originate in the nests of birds or rodents feeding on their blood. If the original nest is disturbed, or the host animal dies, the mites may invade homes.>

    bird mite
    bird mite & human hair (for scale)

    Chigger mites - These tiny biting mites are most often encountered outdoors. They do not invade or become established in homes and are easily washed off before bites are noticed. However, because skin lesions can develop long after the mites are gone the bites may seem like they have appeared for no reason.

    Pyemotes mites - Like chigger mites, pyemotes mites are usually encountered outdoors under very specific conditions. This article discuss how to avoid contact with these mites.

    Scabies mites - These tiny mites burrow into skin causing intense itching. Persistent infections can result if not treated.

    Ticks (yes, ticks are mites) - These are small to fairly large mites that firmly attach to the host animal (including people) and can sometimes transmit disease. Ticks are very unlikely to be the cause of "mysterious bites" because of their relatively large size.

Flies that bite people

    Biting midges - These tiny biting flies (midges, gnats) can be fierce biters annoying both people and livestock.

    Black flies - These small biting flies are more common around fresh, flowing water such as streams and rivers. They occur outside and are unlikely to be the source of "mysterious bites", especially those that occur at night.

    Mosquitoes - These relatively large biting flies can be both annoying and dangerous. Some very serious diseases like malaria and yellow fever are transmitted by mosquitoes and have had a profound impact on human history.

    mosquito drawing
    mosquito (top and side view)

Human lice

    Head lice - Head lice are found on the head usually near the scalp. Eggs (nits) are attached to hairs.

    Body lice - Body lice closely resemble head lice but occur more commonly in clothing. Eggs are laid in clothing which make these lice easier to control in many situations.

    Pubic lice - Pubic lice, also called "crabs", occur in pubic areas and are generally considered to be an STD. Like head lice, eggs (nits) are attached to hairs.

    head louse
    head louse


Fleas (there are many species) tend to be somewhat specific to a particular host animal. The one that most often impacts people and pets is the cat flea. This flea prefers cats and dogs but will also bite people (see this article for life history and control options when homes and pets are infested). Fleas and flea bites can occur, on occasion, even in homes without pets. See the article cited above for more information.

adult flea

Finally, things that can be mistaken for bug bites

Allergies - since the red itchy skin lesions caused by real bug bites are an allergic reaction to proteins in the bug's saliva it should not be surprising that other types of allergies closely resemble bug bites. Food and respiratory allergies cause hives and itchiness that resemble bug bites as well. In fact, allergies are the number one cause of these skin reactions, they are far more common than real bug bites. For airborne allergens like mold spores the new air purifiers with HEPA filters can be very effective at cleaning the air of contaminants, see this article about air purifiers that remove airborne allergens.

Toxic chemicals - such as cleaning solvents and pesticides can cause severe skin lesions in sensitive individuals. Botanical insecticides are generally safer for indoor use and far less likely to cause problems (they work, too!).

Physical irritants - anything from fiberglass splinters to dry skin can cause irritation. In the case of dry skin a simple room humidifier can give fast, inexpensive relief. Dry, itchy skin is mostly a problem during winter months when central heating in our homes tends to dry the air.

Drug side effects - especially stimulants like amphetamines which are notorious for causing outbreaks of skin lesions caused by scratching to relieve the "crawling" sensations; even prescription drugs can cause these same effects.

Emotional stress and anxiety can cause skin lesions that can resemble bug bites. This may be one of the most common causes but also one that people are generally unwilling to accept. Any recent emotional upset or bout of anxiety that coincides with an outbreak of "bug bites" should be considered suspect.

The bottom line - you should not assume that a "bug" is causing the problem unless you can capture and identify one. In the absence of a verified bug your first step should be to consult with a medical professional to rule out some of the other causes such as allergies. The quicker you find the real cause the faster you'll get some real relief.


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Insect Identification

This DK Smithsonian Handbook is an excellent general guide to insect identification (available through Amazon, our Affiliate):

For additional resources see our Insect Identification article.

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