• Insect bites which cause local inflammatory reactions are puncture wounds from insects whose saliva contains concentrated irritant substances such as anticoagulants and enzymes. Symptoms vary depending on the type of insect and the sensitivity of the person who is bitten.

  • The most common bites in Canada are from mosquitoes, flies, fleas and ticks.

  • There are  approximately 3000 species of spiders  in North America and all are poisonous. However,  most of them are too small, don’t have biting apparatuses strong enough to penetrate human skin  or have too little poison to be a threat to humans. There may be a mild reaction at the site of the bite, but any severe reaction from a spider bite is usually delayed from 1 to 8 hours. The two most common species of spiders that are considered health threats are the black widow and brown recluse.  There are no brown recluse spiders in Canada, but there are black widow spiders, some of which may be brought into the country in produce imported from the south. Eighty percent of suspected spider bites have been found to be due to ants, fleas, bedbugs, ticks, mites, mosquitoes and biting flies.

  • Bee and wasp stings are not the same as insect bites. It is important to recognize that the venom or toxin of stinging insects is quite different and the body's reaction to a sting may differ from one species to another. Honey bee stingers remain in the skin. Bumble bees and wasps do not leave their stingers behind and can sting more than one time. Bees are more likely to cause anaphylactic reactions with an incidence of 0.5 to 5% of the population affected.

  • Chance of being bitten by an insect increases with the amount of skin exposed.

  • Some diseases are spread by insect bites. Mosquitoes of the Culex tarsalis species which are active from late June to August are responsible for human infections of West Nile virus in Canada.  Bites from deer ticks (Ixodes scapularis) can cause Lyme disease. Although these are the only significant diseases spread by insects in Canada, other less common diseases can also be tick borne.

For more information and photos:

  • Insect bites usually start as small, itchy red bumps or blisters.

  • Bee and wasp stings usually start as a sharp burning pain which may progress to a red, swollen welt.

  • Bites may progress to larger reactions with inflammation, pain, severe itching, and swelling and in some cases fever, hives and joint pain.

  • Severe reactions (anaphylaxis) may cause facial swelling and trouble breathing.

  • Bites from ants may cause a painful, itchy raised pustule.

  • Location of bite may give some clue as to the type of insect which caused it:

    • Flying insects tend to bite or sting exposed skin areas

    • Flea bites are likely to be on the lower legs and around the waist, often occurring in clusters

    • Bedbugs may bite in clusters, usually around the head and neck

    • Ticks attach themselves as a person brushes past leaves and grasses the ticks are on. Once in contact, they may move to a warm and moist location such as the armpit, groin, back of the knee or hairline, where they burrow into the host's skin and feed off their blood

    • Black fly bites are often along the hairline and around the ears

    • Sand fly bites are usually in clusters around the ankles

Insect bites are diagnosed based on symptoms and history. Rule out the following conditions that may present with similar symptoms:

  • Allergic Reactions - Bites usually occur singly or in clusters. Allergic reactions may cause extensive skin symptoms such as hives on areas other than the site of the bite. Question patient about exposure to new detergents, soaps or shampoos or whether they have eaten something which might cause a reaction. Usually a self-limiting condition that can be treated with antihistamines. Refer to physician for allergy testing if desired.

  • Impetigo (1 to 2 mm fragile pustules and / or honey-colored, crusted erosions) or other bacterial skin infections - can be the consequence of scratching a bite.

  • Folliculitis / boils - infected hair follicles; presenst as red, often itchy, papules and/or pustules at the base of the hair shaft. Subcutaneous folliculitis forms furuncles ( boils) - tender red swellings often with a central pustule.

  • Adverse drug reactions which may present as rash or hives. Question patient on current or recent drug treatment especially antibiotics. Refer to physician if drug reaction to a prescribed medication is suspected.

  • Bed bugs - Bites which recur, especially during cool months may indicate an infestation of bed bugs or other bugs which require professional extermination. Treat and suggest a call to an exterminator.

  • Scabies - papules, vesicles, burrows in finger webs, sides of fingers, wrists, elbows; may be more widely distributed on children; intensely itchy especially at night.
  • Lyme Disease - a rash expanding over the course of a few days and resembling a bulls-eye around the site of the tick bite. May be accompanied by flu-like symptoms. If not treated, may progress to severe joint pain and swelling, cardiac arrythmias and neurological symptoms such as numbness. Refer to physician for evaluation; antibiotic treatment may be required.

  • Tinea corporis (ringworm) - starts as an itchy round spot with a raised, scaly erythematous border that gradually expands outward, leaving the center clear. Lesions may be located on the face, trunk and limbs
  • Venomous spider bites which may cause increased body temperature and blood pressure, profuse sweating, dizziness, blurred vision, nausea, and pain and swelling around the bite within 1 to 8 hours.

Patients with mild to moderate symptoms due to insect bites often do not require further investigation, however a physician assessment should be recommended in the following situations:

  • Anaphylactic reactions

    • May appear as:

      • trouble breathing or swallowing

      • swelling of lips or throat

      • fainting or dizziness

      • confusion

      • rapid heartbeat

      • nausea and cramp

    • Patients presenting with severe or systemic reactions should be sent to the nearest hospital Emergency Department immediately. An epinephrine injection may be required depending on severity.

    • If symptoms not urgent, refer to physician for testing and prescription medication or epinephrine injection device.

  • Family or personal history of serious reaction to insect bites.

  • Multiple bites / stings on widespread areas of the body.

  • If inflammation worsens or lasts longer than 7 days or if the area becomes tender to touch.

  • Suspected adverse reaction to a prescription drug.

  • Unable to confirm patient diagnosis or a more serious condition (see Differential Diagnosis above) is suspected.
Non-pharmacological treatment of insect bites and stings:

For most cases which are not deemed emergency, recommend general first aid measures such as:
  • Application of cold compresses to minimize swelling and slow the spread of venom.

  • Oatmeal baths or baking soda baths to soothe itch.

  • Application of a paste of baking soda and water, left on for 15 to 20 minutes.

  • For stings recommend lying down and lowering stung arm or leg.

  • Removal of honey bee stingers as quickly as possible to stop further venom from being released. Scratch out the stinger with fingernail or something flat. Do not pull it out as this will force more venom into the skin.

  • Prompt and careful removal of ticks - Use tweezers to grasp the tick near its head or mouth and pull gently to remove the whole tick without crushing it. If possible, seal the tick in a jar and take it in to the doctor if you develop signs of illness after a bite. Wash hands and bite area with soap and water. See a doctor if you can’t remove the entire tick.

  • Professional extermination may be required if bites are due to an infestation such as bed bugs.

Over-the Counter Drug Options

  • Oral antihistamines within the first few hours will help to decrease symptoms especially if there are multiple bites or excessive redness or swelling.

    • Any antihistamine will do, but cetirizine has a quicker onset of action (15 – 30 minutes) than loratadine (1 – 3 hours).

    • Diphenhydramine or chlorpheniramine at bedtime may help induce sleep and help to break the itch-scratch-itch cycle, but be aware that sedation may persist into the following day.

  • Ibuprofen or naproxen may help lessen inflammation and swelling as well as pain
  • Acetaminophen may help lessen pain.

  • 0.5% or 1 % (if > 2 years of age) hydrocortisone may produce some decrease in itch and inflammation. Apply 1 to 2 times daily for up to one week.

  • Menthol-containing products or ammonia-containing products help cool the area to reduce pain and itch.

  • Anyone who has had a systemic reaction to a bite or sting should carry an epinephrine injector device.

  • Options not recommended:
    • Calamine creams and lotions may help soothe, but the dried residue may exacerbate the itch in some people.
    • Topical antihistamines may cause sensitization.
    • It is unlikely that topically applied vinegar to neutralize wasp stings will be effective as the venom spreads deep into tissues within a few minutes.

Prescription drug option

  • Hydrocortisone 1% cream, lotion or ointment is indicated for topical therapy where anti-inflammatory, anti-allergic and anti-pruritic activity is required. Hydrocortisone 1% is considered a mild corticosteroid.

    • Note:  Hydrocortisone 1% is Schedule 1 (Rx) only for patients under 2.  Otherwise, it is an OTC product that is not eligible for the minor ailment assessment fee.
  • Dosage:  Adults and children 2 years and older.

    • Apply sparingly to affected area 3 to 4 times a day for 7 days.

    • Application may be reduced to once or twice a day with equal effectiveness.

    • Apply a thin film to clean, dry, affected area and rub in gently.

    • Use sparingly and with caution around eye area.

  • Absorption: Corticosteroids are minimally absorbed from undamaged skin. Small amounts of drug reach the dermis and are then absorbed into the bloodstream.
    • Absorption is greater from the scalp, face, eyelid, armpit and scrotum and is also increased if the skin is inflamed.
      Various vehicles will affect the amount of drug absorbed.
    • Occlusive dressings will increase absorption.
    • Once applied, continued absorption of hydrocortisone may occur, even after washing, due to retention of the drug in the stratum corneum layer of the skin. Because of this retention effect, application may be reduced to once or twice a day from 3 to 4 times a day with the same effectiveness.

  • Creams are more cosmetically acceptable and work best for inflammatory lesions.

  • Topical hydrocortisone should not be applied to tubercular, bacterial or fungal infections of the skin, or to certain viral skin eruptions such as herpes simplex and chickenpox ,or to reactions at vaccination injection sites.

  • Use with caution in patients with skin diseases associated with impaired circulation and in patients receiving other immunosuppressants.

  • Pregnancy: The use of topical corticosteroids is generally considered to be compatible with pregnancy.

  • Lactation: The use of topical corticosteroids is generally considered to be compatible with lactation.
  • Directions for use of hydrocortisone topical products (under prescription drug options above)

  • Advice on avoiding insect bites:

    • Wear light coloured clothing and long sleeves and pants when outside, especially in wooded areas and tall grasses.

    • Be aware that dawn and dusk are when mosquitoes are most active.

    • Stay away from wasp nests and keep food inside or well covered.

    • Wear insect repellent (details under Insect Repellant) / protective clothing when outdoors especially during West Nile Virus season June to September.

    • Check yourself and pets regularly when returning from areas that may be tick habitats.

  • Suggest that people carry epinephrine if they've ever had a systemic reaction or had a large local reaction with extensive swelling. Up to 10% of these patients can have a systemic reaction the next time they're stung.

  • Seek professional advice to get rid of infestations such as bed bugs.

  • Bites from mites or fleas on pets may require veterinary treatment of the animal. Treat and suggest having animals treated by a veterinarian.
  • Expect relief from symptoms within 24 hours. If no improvement or symptoms worsen, consult pharmacist or physician.

Assess Benenfit:

  • No follow-up usually required.

  • Advise patients to contact their doctor if symptoms do not resolve in 7 days.

Adverse Effects

  • Rare with mild topical corticosteroids used for short periods. There is little risk of skin thinning when used for up to 4 weeks.

  • Systemic effects are extremely rare and attributed to prolonged use of potent steroids to large areas.

  • Allergic reactions are rare with topically applied steroid products and are usually attributed to preservatives in the product base. If there are signs of an allergic reaction, discontinue use and treat appropriately.

  • Use repellents that have a Pest Control Produce registration number
  • Use only repellents labelled for use on humans
  • Health Canada supports the use of products containing DEET with these guidelines:
    • Adults and children > 12 years old - DEET 30% should be effective for 6 hours against mosquitoes.
    • Children > 2 to 12 years old – DEET 10% should be effective for 3 hours against mosquitoes. May reapply up to 3 times a day.
    • Children > 6 months to 2 years old - DEET 10% should be effective for 3 hours against mosquitoes. APPLY ONLY ONCE A DAY.
    • Infants < 6 months old – Do not use DEET containing products. Use a mosquito net for protection.
  • Health Canada also supports use of Icaridin:
    • Adults and children 6 months and older: May use up to 20% Icaridin for 6-8 hours of protection.
    • Infants <6 months old: Do not use icaridin.  If travelling to an area where bites are more than "nuisance" bites, 10% icaridin is reasonable.
  • Health Canada also supports the use of products containing P-methane 3, 8-diol (e.g. Off! Familycare Eucalyptus lotion™) which provide up to 2 hours protections against mosquitoes and 5 hours against black flies.  These may be reapplied up to twice in a day. Not for use under 3 years old.
  • Products containing soybean oil 2% blocker repellent (e.g., Bite Blocker™) provide protection up to 3.5 hours for mosquitoes and 8 hours against black flies. There are no age limits or limits to frequency of application.
  • Registered products containing citronella may provide up to 2 hours of protection against mosquitoes. Not for use in chldren < 2 years old. These remain on the market until a final decision about their safety is made by Health Canada.

For all insect repellent use:

  • Read entire label and follow directions carefully. 
  • Be aware of age restrictions and frequency of applications allowed.
  • Apply sparingly on exposed skin and on top of clothing. Do not use under clothes.
  • Wash hands to avoid getting in eyes. Rinse eyes with water immediately if needed.
  • Use in well ventilated areas or outdoors only.
  • Do not apply sprays near food.
  • Do not spray directly on to face. Spray on hands and then apply to face.
  • Keep out of reach of children and supervise their application.
  • If a reaction to a repellent is suspected, wash off, seek medical attention and take container with you.

(< 2 years of age)




  • pseudoDIN: 00951089
    • Max of 8 claims per 365 days per patient

  • May prescribe sufficient quantity to treat up to 7 days, no refills.
  1. C-Health - Insect bites and stings (Free access)
  2. Saskatchewan HealthLine online - Insect bites and stings and spider bites (Free access)
  3. Canadian Pharmacist’s Letter Aug 2008 Vol: 15 15(8):240815 (Subscription required)
  4. Emedicine.com - Insect bites (Free access)
  5. Dynamed – insect bites. (Subscription required)
  6. UpToDate – insect bites (Subscription required)

No part of this work may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the copyright holder. For copyright permission requests, please contact druginfo@usask.ca.

Prepared by medSask
Reviewed by Dr. D. G. Bishop, Family Physician
Funded by the Saskatchewan College of Pharmacists
Posted May 2010. Updated March 2016