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Unknown & Mysterious Bug Bites

- What's biting me??? -

Summary: A number of insects and mites can bite and leave a red, swollen, itchy bite mark. There are also many other causes of skin irritation that can be mistaken for bug bites. In many cases, therefore, what appears to be a bug bite may in fact be caused by something else.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)
my resume

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 (see this image gallery of the Top 12 Insects & Mites That Bite) and fewer still for which we are the primary host. Take a look at the list of insects and mites below that bite people. If you can not clearly identify one of these as the cause of your bites then consider some of the other reasons. Notice that the bites are all very similar in appearance (red, itchy bumps) making diagnosis from the bite alone nearly impossible.

mysterious bug bites

Mysterious "bug bites" on wrist and arm; many different agents can cause the skin to erupt into red, swollen patches that may appear to be bug bites.

Causes of real bug bites (please check this list first)

  • Bed bugs - large, red, splotchy, itchy, mosquito-like bites
  • Black flies - small to large, red, itchy bites, sometimes mosquito-like
  • Fleas - red, itchy, bites often around ankles, lower legs
  • Lice
    • Head lice - red, itchy bites on back of neck and head, more common in school-age children
    • Pubic lice - red, itchy bites in pubic (groin) area, highly contagious, pubic lice are "crab-like" in appearance
    • Body lice - red, itchy bites on scalp, groin or areas in contact with clothing, depending on species

  • Mosquitoes - red, itchy bumps
  • Scabies mites - red bumps and burrows may be visible, intensely itchy
  • Ticks - tick often found attached to skin marked with red halo around bite

Things that can be mistaken for bug bites

If you have a bug to id or need a specific pest control recommendation see our Insect Id service. If, however, you can't catch a real bug then the cause may not be insects or mites at all. The most common causes of red, itchy skin are:

  • 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 so closely resemble bug bites. Food and respiratory allergies cause hives and itchiness that closely resemble bug bites. 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 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, or, for example the Winix PlasmaWave 5500 Air Cleaner.

  • Toxic chemicals - such as cleaning solvents and pesticides can cause severe skin lesions in sensitive individuals. Botanical insecticides are generally safer for indoor use.

  • 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. See for example the Honeywell Germ Free Cool Mist Humidifier.

  • 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.

  • Extreme emotional stress and anxiety can cause these skin lesions as well.

do it yourself pest control products and supplies

Finally, I believe that many of the "mysterious bug infestations" that afflict so many people are being caused by respiratory and/or food allergies**. These allergies can be easily treated once a proper diagnosis is made. There are of course other underlying medical conditions that can mimic the skin eruptions of insect and mite "bites", and some of these conditions can be serious.

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 relief.

**This information should not be considered medical advice; always check with your own medical adviser for specifics regarding your health following a complete exam.

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Mission: To provide accurate, up-to-date and unbiased information for solving common insect and mite problems around your home, business and landscape using least-toxic methods.

Jack DeAngelis, PhD,  , email:  [email protected]

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