Linear lesions may occur in groups of three (or four) and have been called "breakfast, lunch, and dinner (and a snack)."

INSECT BITES (PAPULAR URTICARIA, BUG BITES)

The term papular urticaria refers to the urticarial bumps that occur with insect bites. Blisters are common as well. Humans are often bitten by various insects, e.g., mosquitos, spiders, etc., which induces an immune response at the bite site.

• Blisters
• Red, itchy bumps.
• Red nodules.
• Annular plaques, targetoid lesions or rings.
• Typically, because the patient is the only one bitten in the family, he/she "is certain it is not bugs!"

The most common response is an intensely urticarial papule or nodule. Lesions may have a scab or disruption in the center from the bite. Targetoid or bullous lesions may be seen. The lesion usually occurs in an exposed area. Linear lesions may occur in groups of three (or four) and have been called "breakfast, lunch, and dinner (and a snack)." Bullous lesions are usually tense, filled with clear fluid, and with an uninflamed base. Asymmetry is almost always part of the pattern, helping with the diagnosis.

If lesions continue to develop, then ongoing exposure in the house must be considered. Has anyone in the family stayed in a hotel recently or has anyone slept over recently (bed bugs)? Any nests in the eves (bird mites)? Are there any animals in the house?

Potential reservoirs in the house for arthropods or their hosts include:

• Beds and floorboard (bed bugs).
• Webs, walls (spiders).
• Bird and birds nests in the eaves or other areas near the the house (bird mites).
• Worm-eaten wooden structures (e.g. Pyemotes ventricosus is a parasite of the woodworm. Look for example in wooden furniture. The furniture beetle is one example of a host for such mites.)
  
  • Pets (e.g. the cat mite, cheyletiella, fleas)
  • Plants (e.g. Monomorium destructor, commonly known as the Singapore ant and Solenopsis fugax, a fire ant)
  • Mould on the walls (e.g. Glycyphagus domesticus or the storage mite, furniture mite or food mite).

Differential Diagnosis of red, itchy bumps

Sometimes the patient is adamant that s/he is not being bitten. In that case, the clinician must always consider other possibilities. These include bacterial folliculitis (often pustules are present and the lesions are more painful than itchy) and lymphomatoid papulosis. A biopsy may be indicated.

A large urticarial ring is one dramatic presentation of an insect bite.

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