What bit me? Match your bites to a pattern

Three questions sort most bites. Where on your body are they? Are they alone, in a group, or in a row? And when did you first notice them: right after time outside, or after a night's sleep? Write the answers down. A clinician will ask when the bites happened, how many there were, and how soon the symptoms started (Cleveland Clinic).

Arrangement alone won't settle it. Fleas, bed bugs, and chiggers can all leave bites in a line or cluster, and it isn't always easy to tell which bug made a mark (Cleveland Clinic). What separates them is where on your body the bites are and when they showed up, which is why the table above is built around place. The sections below say which places and timings go with which biter.

Fleas are tiny, flat, and dark brown or black. Their bites are small discolored bumps, sometimes with a ring around them, in a line or a cluster on the feet, calves, and ankles. They rarely show up above the knee unless you've spent a long time sitting or lying down, and they don't swell as large as mosquito bites (Cleveland Clinic). If your pet has fleas and you have bites on your legs, they're likely flea bites. To check, part the pet's fur and look at the skin around the ears, neck, back, and belly. The flea bite guide covers what to do once you're sure.

Chiggers are mites too small to see well. They live in grassy or wooded areas, usually near water, climb from your clothing onto your skin, and feed where the two press together: waistbands, sock lines, behind the knees, and skin folds. The result is a speckled line of very itchy red spots, and you may not feel anything for up to three hours after the contact (Cleveland Clinic). Chiggers live outdoors, so new bites after a week spent only indoors point to another cause. To choose between the two, ask what came before: a pet with fleas points to fleas, and a day in tall grass followed by a line of dots at your sock line or waistband points to chiggers.

Bed bugs inject a numbing fluid, so you don't feel the bite. Most people see the marks one to several days afterward, and in some people it takes up to 14 days. The marks look like mosquito or flea bites, a slightly swollen red area that may itch, and they can be random or in a straight line (CDC). That delay is one clue: a mosquito bite usually puffs up within minutes (CDC), while bed bug marks tend to appear a day or more later.

Because the marks look like other bites, look for the bugs themselves. Shed skins, bugs in the folds of mattresses and sheets, rusty-colored blood spots on the mattress or nearby furniture, and a sweet musty odor are the signs. Bed bugs tend to live within 8 feet of where people sleep, in mattress seams, box springs, bed frames, and headboards (CDC). A flashlight along the seams and the headboard tonight tells you more than the bites do. The bed bug bite guide covers what to do if you find them.

Scabies isn't a bite in the usual sense. The mite burrows into the top layer of skin, where it lives and lays eggs, instead of feeding and leaving. It causes intense itching that is worse at night, with a pimple-like rash between the fingers, in the folds of the wrist, elbow, knee, or armpit, and on the waist, buttocks, and shoulder blades. You may see tiny burrows, the tracks a female mite leaves while tunneling just under the skin (CDC).

It spreads mostly through long skin-to-skin contact, and less often through shared clothing, towels, or bedding. The first time someone has it, the itch can take four to eight weeks to start, and the person can pass it on in the meantime. Treatment needs a prescription, and everyone in the household who has had close contact is treated at the same time (CDC). The CDC's advice is to seek medical attention if you suspect it, so if this pattern fits, see a clinician instead of guessing.

A day after a mosquito bite, the puffiness can turn into a hard, itchy, reddish-brown bump, a patch of small blisters, or a dark spot that looks like a bruise (CDC). You can sometimes see a small dark dot in the center where the bite went in (Cleveland Clinic).

If something is still attached, it may be a tick. Ticks have eight legs, range from light to dark brown, and some are too small to see easily. You may not feel the bite, and the tick can stay on for several days (MedlinePlus). On people they're most often found in the groin, armpits, and scalp, so check there first. If you find one, grip it with fine-tipped tweezers close to the skin and pull upward with steady, even pressure, and don't crush it (FDA).

Pain at the moment it happens can be a sting or a horsefly bite. A bee sting brings instant, sharp burning pain, a welt, and swelling (Mayo Clinic), and it leaves a small mark where the stinger went in, which may still be stuck in the skin (NHS). A horsefly bite is large and painful, may bleed, and often gets infected (NHS).

A chart or a quiz narrows the list, and neither confirms a bug. The What Bit Me? quiz asks the same clues one at a time: where the mark is, what pattern it makes, how it looks, what it feels like, and when you first noticed it. What settles the question is the bug itself or a sign of it, like a tick on your skin, a flea on the dog, or shed skins in the mattress. Naming the bug when you can helps you and your clinician plan treatment and watch for complications (Cleveland Clinic).

Five short notes make any later guess, yours or a clinician's, much easier.

• Where each bite is, and whether the other side of your body has them too.
• The count, and the shape they make on your skin.
• The day and time you first noticed them.
• What came before: time in grass or woods, a night in a new bed or hotel, a pet on the furniture.
• Whether anyone else in the home has marks.

Symptoms in other parts of your body are a reason to see a provider. So are fever, chills, body aches, joint pain, swollen lymph nodes, or a round bull's-eye rash in the two weeks after a bite. A red streak running from the bite, blisters, or pus are the signs of a skin infection (Cleveland Clinic).

Get care now, and call 911 or your local emergency number, if you have trouble breathing, swelling of the lips, face, eyelids, or throat, dizziness or fainting, hives, or nausea and vomiting. Any one of those is enough to call (Mayo Clinic).

If the chart leaves you with two guesses, photograph the bites, or the bug if you found one, in the BiteSight iPhone app. If you don't have an iPhone, the same photo tool works on the web. There's no Android app yet.