This has been a banner year for insect bites, and I’ve been hearing many more complaints from patients. It’s likely that our last long wet winter, followed by warm weather, is responsible.
Which insects are causing the problem, and what can we do about it?
■ Mosquitoes are the most common source of bites. In fact, there is a new invasive and aggressive species found here in Southern California called Aedes aegypti, They are black with white stripes, and don’t behave like typical mosquitoes. They will aggressively follow their victim, and bite during daytime hours, unlike the typical dusk biting behavior of most other mosquitoes.
For the most part, mosquitoes are found near standing water, even very small quantities of water, where they breed. Their bites cause local pain, itching, swelling and redness. Typically, within 20 minutes there is an itchy bump. It peaks within two to three days, and then goes away.
Some people, particularly young children and highly allergic people, can develop dramatic swelling surrounding the bite, and even a low-grade fever (often mistaken for cellulitis).
Mosquitoes pose an additional problem; they can transmit serious diseases. Locally, there have been cases of West Nile virus, St. Louis encephalitis, and Zika virus. Worldwide, they also transmit malaria, yellow fever, dengue fever, La Crosse encephalitis, and chikungunya virus.
■ Spider bites pose a variety of problems, depending on the variety of the spider. Symptoms of bites can include itching, rash, bite site and muscle pain, sweating, trouble breathing, headaches, nausea and vomiting, fevers, chills, anxiety, restlessness, and even high blood pressure.
Venomous spiders found in the United States include the black widow, brown recluse, and hobo. Although they are especially dangerous to those who work outdoors, we all know that they do occasionally find their way inside.
Stay calm, wash the skin with soap and water, apply cold water or ice, elevate the bite, attempt to identify the type of spider, and see your doctor if necessary.
■ Ticks can transmit several infectious diseases, including Lyme disease (which is rarely seen in California).
■ Flea bites are usually only a nuisance. It’s possible for the site to become infected, though, by scratching that annoying itch!
■ Houseflies can’t actually bite. They can, however, transmit intestinal infections in conditions where the water and general hygiene are poor.
Some insects can cause a general (systemic) allergic reaction. These are uncommon but can be caused by mosquitoes, ticks, fleas, blackflies, deerflies, louse flies, horseflies, centipedes, kissing bugs, and notably…by the sting of a bee.
The most serious (but rare) generalized allergic reaction is anaphylaxis, with hives, wheezing, vomiting, low blood pressure, and even loss of consciousness. Anaphylaxis needs immediate treatment with epinephrine. Anyone with a history of anaphylaxis should see an allergist for further education and evaluation, and carry an epinephrine autoinjector.
How much trouble should we go to in order to prevent insect bites? It depends on how significant the risk is. If we travel to a foreign country where a mosquito bite can lead to malaria, then it is critical to protect ourselves.
Strong chemical products (like DEET and Permethrin) are very effective. However, milder insect repellents may be enough in areas with lower levels of disease. Botanical oils, including sandalwood, geranium, and soybean, have been used to repel mosquitoes and ticks. However, they aren’t nearly as effective as DEET or permethrin.
Of course, for those simple insect bites, treatment focuses on the relief of symptoms. Wash the area with soap and water. Reduce any local swelling with ice or a cold pack. Reduce any itching with a topical cream (containing calamine, steroids, or pramoxine), or an oral medicine (products like Claritin or Dimetapp can help during the day, and an antihistamine like Benadryl can help at night).
Whether at home or away, know your risks, and take measures as needed to protect yourself.
December 14, 2017
Paging Dr. Frischer: Bug Bites
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