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Insect Bites and Stings

Edited by Claire Butler

With summer here, we can finally leave our houses, enjoy the fresh air, and safely see some of our friends the lockdowns have kept us away from. We are not the only ones coming out for the sun, though. Insects, too, enjoy the summer heat, and a bite or a sting from one of these creatures may not only ruin your day but could require medical attention. Would you be able to recognize a bite or sting and know how to respond?

Insect Bites

Spiders, ticks, mosquitoes, and bed bugs are just a few of the many insects that bite.

Spiders rarely bite humans, and although most spiders are venomous, few of them deliver enough venom in a bite to cause symptoms in the body. Spider bites usually cause a stinging feeling that is followed by swelling in the area, itching and inflammation.

Ticks attach to the skin with specialized mouth parts and feed until they are engorged with blood. They are most often found in warmer areas of the body such as the groin, armpit and scalp. The most common reaction to a tick bite is a red papule at the bite site, but swelling, blistering, bruising, itching or infections may develop. Certain ticks carry bacteria which may transmit diseases to humans. The black-legged tick (deer tick) and the Western black-legged tick may transmit Lyme disease if attached to the body for longer than 24 hours, and in Western Canada, the Rocky Mountain wood tick carries the bacteria that causes Rock Mountain Spotted Fever.

Mosquitoes injecting salivary secretions into the small blood vessels near the surface of the skin, commonly causing local reactions. These reactions involve redness, swelling and intense itchiness. The red, itchy papules develop within hours and then subside slowly over a few days. Like ticks, there are many diseases (e.g., malaria, Zika virus) that can be carried by infected mosquitoes, with the most relevant in Canada being the West Nile virus. May through October are the peak times for West Nile virus. Many people infected with West Nile virus do not become sick, but if symptoms do develop, they usually begin within 2-15 days of being infected. Mild cases usually cause flu-like symptoms (fever, body aches, headache), and possibly rash or swollen lymph glands.

Finally, bed bugs feed on blood by piercing the skin, which can cause red, itchy lesions at the location of the bite. Bites are usually on the arms and legs in clusters of 3-5 which appear in a line, curve, or zigzag pattern. There may be specks of blood found on bedding or pyjamas. Bed bugs are attracted to humans by warmth and carbon dioxide. They generally feed just before dawn and hide during the daylight hours within mattresses, box springs, walls, or behind headboards. As of now, studies do not definitively show that bed bugs carry diseases.

Insect Stings

There are three families of stinging insects: bees (bumblebees, honeybees), vespids (yellow jackets, wasps, hornets), and stinging ants (fire ants). The most common reaction to a sting is a local skin reaction that begins within 4-48 hours, causing pain, redness and swelling at the site. There may occasionally be an extensive local reaction with swelling over a large area (eg. a limb). Systemic reactions such as headache, fever, nausea, and vomiting are more likely with multiple stings from the same insect as well as repeated stings with a few months. The most serious reaction to insect stings is anaphylaxis, which can occur within minutes or up to several hours after the initial sting. Anaphylaxis requires immediate emergency attention

Bee, Wasp, Hornet, Yellow Jacket Stings

Fire Ant Sting


Prevention of Stings

The best thing you can do to prevent getting stung by an insect is to limit the time spent outdoors at dusk and dawn, as that is when the majority of insects are out and about. You should also avoid situations where insects might feel threatened, such as near nesting areas, hives, or when removing nests, as stinging insects sting in self-defence. Scented cosmetics, perfumes, hairsprays that can attract insects should also be avoided, and long clothing that covers as much skin as possible should be worn. Use caution when eating outdoors and ensure drinks are covered to avoid ingesting wasps or bees.

Prevention of Bites

Most biting insects like to inhabit tall grasses, marshes, swamps, and bushy areas. That being said, these areas should be avoided as much as possible. If not possible, long light-coloured clothing should be worn for easier insect detection and quick removal. Pants and shirts should be tight at the ankles and wrists or tucked into socks and gloves. Infants less than 6 months old in particular should be covered by long clothing and mosquito netting, as well as those travelling to areas where mosquito-borne illness (such as West Nile Virus) is endemic. If you are looking for a way to reduce the local mosquito population, the most effective way is by eliminating sources of standing water such as rain barrels, clogged gutters, and bird baths. Once returning indoors, you should inspect your clothing and exposed skin areas for any insects. Again, it is best to avoid time spent outdoors during dusk and dawn.

Bed bugs can be avoided by using a magnifying glass and thoroughly checking headboards, mattresses, box springs, and furniture. Bed bugs are oval shaped, approximately 5 mm in length, and range in color from light yellow to reddish brown. Live bedbugs can sometimes be seen by using a flashlight just before dawn when they are the most active. It is important to check hotel rooms, new environments and any garage sale or second-hand items brought into the home. A combination of chemical pesticides and nonchemical methods can be used to eradicate them, such as vacuuming, applying heat (>49 °C) or steam for at least 2 hours to the mattress, exposing it to cold temperatures (<18°C) for at least 4 days, and using mattress encasements.

Insect Repellents

Insect repellents (AKA “bug spray”) works to repel biting insects such as mosquitoes, black flies, and ticks. However, they do NOT work against stinging insects. Insect repellent should be applied directly to clothing and exposed skin. For the face, repellent should first be applied to the hands, which can then be used to apply it to the face. Be sure of avoid the eyes and mouth!

Below, we list some of the most common ingredients in insect repellents and what they are used for:

  • DEET: Effective against mosquitoes, black flies, ticks, chiggers and fleas

  • Icaridin/picaridin: Effective against mosquitoes, ticks, and black flies

  • Oil of lemon eucalyptus/PMD: Effective against mosquitoes, biting flies, and gnats (not ticks)

  • Oil of Citronella: Tested against mosquitoes only

  • Soybean Oil: Effectiveness against ticks is approximately equal to DEET 10%

  • Metofluthrin: Effective against mosquitoes and black flies


At--Home Remedies

The first thing you should do when you notice an insect bite or sting is to remove the insect or stinger to decrease the reaction as soon as possible. Stingers can be scraped off with a fingernail, tweezers or credit card. Ticks should be removed slowly with tweezers, grasping close to where the head contacts the skin, and pull straight up. The next step is to wash the area with warm water and soap to prevent infection. If the area is itchy, you can apply ice or a cool compress for up to 10 minutes at a time. It’s important to avoid scratching the area, as it can damage the skin and cause an infection.


There are a few different medications that can be used depending on what symptoms are present following the insect bite or sting. If you are experiencing pain, acetaminophen, ASA or ibuprofen can be taken. For itching, you can use topical products containing local anesthetics such as benzocaine, lidocaine, or pramoxine. Topical corticosteroids such as hydrocortisone may be used to relieve itchiness, swelling and redness in mild to moderate local reactions to insect bites or stings. Oral antihistamines such as cetirizine can be used to relieve itching, pain and inflammation from insect stings. Topical antihistamines such as diphenhydramine are less effective than oral antihistamines and are not recommended.

When to See a Doctor

You should make an appointment to see your physician if any of the following occur:

  • A rash develops around the bite or sting

  • The bite reaction spreads to a large area (whole arm or leg)

  • The reaction is unresponsive to self-treatment after 7 days

  • There are signs of infection at the site

  • An unusual reaction around a bite develops, such as a purplish colour or blisters

You should visit the emergency department if you develop any of the following within a few minutes to 30 minutes after being bitten or stung:

  • Red flush or itching all over body

  • Chest or throat tightness (difficulty breathing)

  • Hives

  • Nausea, vomiting, abdominal cramps

  • Dizziness, fainting

  • Hoarse voice or swelling in throat (difficulty swallowing)

  • Changes in heart rate

The next time you plan to go outside, be sure to remember the strategies discussed in this article to stay protected from insect bites and stings, and the diseases they may carry!

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  1. DerSarkissian C. Spider Bites: What You Need to Know.; 2019. Accessed June 25, 2021.

  2. Kleiman N. Insect Bites and Stings. In: Compendium of Pharmaceuticals and Specialties. Canadian Pharmacists Association. Updated September 27, 2018. Accessed June 25, 2021.

  3. Lyme Disease Can Be Diagnosed by 'Bull's Eye' Rash Alone.; 2019. Accessed June 25, 2021.

  4. Miller K. The Best Way to Treat a Tick Bite, According to Dermatologists.; 2021. Accessed June 25, 2021.

  5. Odom M. Understanding Insect Bites and Spider Bites - Treatment.; 2007. Accessed June 25, 2021.

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