Insect bites
By Richard Haber, MD
Summer is upon us, and insects, wasps and bees are out in full force. Fortunately, most of the insects we encounter don’t carry disease. The anopheline mosquito, Aedes aegypti, spreads malaria in tropical countries. The deer tick Ixodes scapularis, the vector for Lyme disease, is found mainly in the American eastern or Pacific coast states and contiguous Canadian areas.
West Nile fever, while transmitted by mosquitoes, is usually a selflimited flu-like infection that rarely induces severe disease, except in elderly or immunocompromised individuals.
The buzz and the sting
The buzz and the sting
The insects that most plague us are the mosquito and black fly, very common and annoying. The first exposure triggers no reaction, but after repeated bites and injection of bug saliva, an immediate hypersensitivity develops and a wheal appears within minutes, soon followed by a pruritic papule. Children may experience fairly extensive swelling, especially those under age 3, because of the greater water content of the dermis. This is particularly evident if a bite has occurred around the eye or at the wrist or ankle, or if the child has been the target of several bites concurrently.
Orbital swelling is often confused with periorbital cellulitis, a serious infection, but a cold compress and an oral antihistamine such as diphenhydramine will provide relief and help distinguish between the two. Watch for secondary infection caused by scratching — spreading erythema, purulent discharge or crusting. Infected insect bites may need systemic antibiotic treatment, and in my experience, black flies are the culprit more often than not. Of the stinging insects, we find Hymenoptera apidae (honeybees, bumblebees) and vespidae (yellow jackets, hornets and wasps). Yellow jackets are more aggressive and attracted by human food, so they’re most frequently to blame.
Immediate treatment consists of cold compress and analgesia. In the case of a honeybee, remove the stinger and venom sac left in the skin by scraping with the blade of a knife. Bumblebees rarely bother people, and the stinger stays with the insect. Local reaction to Hymenoptera bites may extend to a diameter of ≥ 10 cm and last for several days. Urticaria and angioedema can develop, and most seriously, anaphylaxis. For the latter two, it’s necessary to immediately administer epinephrine, systemic steroids and antihistamines, and later refer to an allergist for further assessment. If found to be truly allergic, the child will require an automatic adrenaline dispenser, such as an EpiPen or Twinjet.
Bug repellents
Bug repellents
Encourage parents and camp staffers to take insect habits into account — avoiding scented bath products, bright clothing, and activities in infested areas early in the morning or evening. Infants in strollers can be protected with mosquito netting.
For the older kids, if cover-ups aren’t sufficient, insect repellent with a DEET content of < 10% is acceptable. Recently the American Academy of Pediatrics has suggested DEET as high as 30%, but because of toxicity, it should be applied sparingly and infrequently, no more than once a day.
Richard Haber, MD, FAAP, FRCPC is Director of the Pediatric Consultation Centre at the Montreal Children’s Hospital, McGill University, in Montreal, Quebec. He is also an associate professor of pediatrics at McGill.
