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Insect Bite


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Female Mosquito
Female Mosquito :: CDC PHIL :: (click image to see Copyright)


  • Itching, pain, or swelling from an insect bite

  • Itchy Insect Bites: Bites of mosquitoes, chiggers (harvest mites), fleas, and bedbugs usually cause itchy, red bumps

  • Painful Insect Bites: Bites of horseflies, black flies, deer flies, gnats, harvester ants, blister beetles, and centipedes usually cause a painful, red bump. Within a few hours, fire ant bites can change to blisters or pimples


  • Tetanus vaccination after an insect bite is not necessary.


  • No-see-ums are tiny bugs that are about 1/10 - 1/15 of an inch (0.16 -0.25 cm). They can pass easily through screens. They are attracted to light. They are most active at sunset.

  • Other Names:They are also called biting midges, punkies, or sand flies.

  • Habitat: Adults live in wet sand. They are especially common along the seashore and shores of rivers and lakes. They lay their eggs near standing water (margins of ponds, ditches, lakes, muddy edges of a salt marsh).

  • Symptoms: The initial bite is generally painless. But within 12 hours the bite mark becomes a small red spot that is intensely itchy. Some sensitive people can develop a larger reaction with a swollen itchy spot (hive) 1-2 inches in diameter (2-5 cm). Scratching makes the itching last longer.

  • OTC Treatment for Itching: Topical hydrocortisone may help; anthistamines reduce the itching.

  • Prevention: No-see-ums cannot bite through clothing, thus good advice is to wear long pants and long-sleeved shirts. Insect repellents containing DEET also seem to be effective in preventing bites.


  • Common chiggers are very tiny bugs that are about 1/150 of an inch (0.017 cm) in size.

  • Other names: They are also called harvest mites, red mites, jiggers, or redbugs. They can easily go through screens.

  • Habitat: Tall grass, berry patches, edge of woods.

  • Symptoms: The main symptom is intense itching and this peaks on day 2. There are usually tiny red bumps or small hives. Tiny bumps may last for 1-2 weeks.

  • OTC Treatment: Topical hydrocortisone may help; anthistamines reduce the itching.

  • Prevention: Avoid areas where chiggers are known to be. Insect repellents containing DEET also seem to be effective in preventing bites.

Bed Bugs

  • Common Bed bugs are small visible blood-sucking bugs that are about 1/4 an inch (7 mm) in length.

  • Habitat: During the day bed bugs hide in the corners of mattresses, bed crevices, floors, and walls. At night the bed bugs come out of hiding and feed on their preferred host, humans. The common bed bug is found worldwide.

  • Symptoms: There is no pain while the bed bug is biting. However, later small red bumps or large itchy wheals (2-20 cm) may develop at the bite site. Occasionally blisters (bulla) can occur at the bite site.

  • OTC Treatment: Topical hydrocortisone cream and oral anthistamines help reduce the itching. Watch for signs of infection.

  • Prevention: Avoid hotels and hostels where bed bugs have been reported. Check along corners of bedding or mattresses for the presence of these bugs. Wash linens once a week in hot water. DEET and permethrin are effective against bed bugs.

If not, see these topics

First Aid:

FIRST AID ADVICE for Anaphylaxis - Epinephrine (pending EMS arrival):

  • If the patient has an epinephrine autoinjector, the patient should use it now.

  • Use the autoinjector on the upper outer thigh. You may give it through clothing if necessary.

Epinephrine is available in autoinjectors under trade names: Epi-Pen, Epi-Pen Jr, and Twinject. Epi-Pen is a single injection. Twinject has a second injection that can be used if there is no improvement after 5 minutes.

FIRST AID ADVICE for Anaphylaxis - Benadryl (pending EMS arrival):

  • Give antihistamine orally NOW if able to swallow.

  • Use Benadryl (diphenhydramine; adult dose 50 mg) or any other available antihistamine.

FIRST AID ADVICE for Anaphylactic Shock (pending EMS arrival):

  • Lie down with feet elevated.


When to Call Your Doctor

call 911

Call 911 Now (you may need an ambulance) If

  • Passed out (fainted)

  • Difficult to awaken or acting confused

  • Wheezing or difficulty breathing

  • Hoarseness, cough or tightness in the throat or chest

  • Swollen tongue or difficulty swallowing

  • Previous severe allergic reaction same insect bite (not just hives or swelling)

  • Note: Symptoms above may indicate anaphylaxis. Anaphylaxis usually starts within 20 minutes, and always by 2 hours following a sting. See First Aid.

call now

Call Your Doctor Now (night or day) If

  • You feel weak or very sick

  • Hives or swelling elsewhere on the body

  • Severe bite pain and not improved after 2 hours of pain medicine

  • Redness, red streak, or very tender area (to touch), and you also have a fever

call within 24 hours

Call Your Doctor Within 24 Hours (between 9 am and 4 pm) If

  • You think you need to be seen

  • Red or very tender (to touch) area, and started over 24 hours after the bite

  • Red or very tender (to touch) area, getting larger over 48 hours after the bite

call within 24 hours

Call Your Doctor During Weekday Office Hours If

  • You have other questions or concerns

  • Scab drains pus or increases in size and not improved after applying antibiotic ointment for 2 days

home care

Self Care at Home If

  • Normal insect bite and you don't think you need to be seen

  • Scab drains pus or increases in size and you don't think you need to be seen



Treatment for Insect Bites

  1. Local Treatment - Itchy Insect Bites (including all mosquito bites)

    • Apply calamine lotion or a baking soda paste.

    • If the itch is severe, use 1% hydrocortisone cream. Apply 4 times a day until the itch is less severe, then switch to calamine lotion.

    • Try applying firm, sharp, direct, steady pressure to the bite for 10 seconds. A fingernail, pen cap, or other object can be used.

  2. Oral Antihistamine Medication for Severe Itching: Take an antihistamine by mouth to reduce the itching. Diphenhydramine (Benadryl) is a good choice. The adult dosage of Benadryl is 25-50 mg by mouth and you can take it up to 4 times a day.

    • Do not take antihistamine medications if you have prostate enlargement.

    • Antihistamines may cause sleepiness. Do not drink, drive or operate dangerous machinery while taking antihistamines.

    • An over-the-counter antihistamine that causes less sleepiness is loratadine (e.g., Alavert or Claritin).

    • Read the package instructions thoroughly on all medications that you take.

  3. Local Treatment - Painful Insect Bites

    • Rub the bite for 15 to 20 minutes with a cotton ball soaked in a meat tenderizer solution. This will usually relieve the pain (Caution: don't use near the eye).

    • If not available, use a baking soda solution on a cotton ball.

    • If neither is available, apply an ice cube for 20 minutes.

  4. Pain Medicines:

    • For pain relief, take acetaminophen, ibuprofen, or naproxen.

    Acetaminophen (e.g., Tylenol):

    • Take 650 mg by mouth every 4-6 hours. Each Regular Strength Tylenol pill has 325 mg of acetaminophen.

    • Another choice is to take 1,000 mg every 8 hours. Each Extra Strength Tylenol pill has 500 mg of acetaminophen.

    • The most you should take each day is 3,000 mg.

    Ibuprofen (e.g., Motrin, Advil):

    • Take 400 mg by mouth every 6 hours.

    • Another choice is to take 600 mg by mouth every 8 hours.

    • Use the lowest amount that makes your pain feel better.

    Naproxen (e.g., Aleve):

    • Take 250-500 mg by mouth every 12 hours.

    • Use the lowest amount that makes your pain feel better.

    Extra Notes:

    • Acetaminophen is thought to be safer than ibuprofen or naproxen in people over 65 years old. Acetaminophen is in many OTC and prescription medicines. It might be in more than one medicine that you are taking. You need to be careful and not take an overdose. An acetaminophen overdose can hurt the liver.

    • Caution: Do not take acetaminophen if you have liver disease.

    • Caution: Do not take ibuprofen or naproxen if you have stomach problems, kidney disease, are pregnant, or have been told by your doctor to avoid this type of medicine. Do not take ibuprofen or naproxen for more than 7 days without consulting your doctor.

    • Before taking any medicine, read all the instructions on the package

  5. Antibiotic Ointment: If the insect bite has a scab on it and the scab looks infected, apply an antibiotic ointment 4 times per day.

    • Cover the scab with a Band-Aid to prevent scratching and spread.

    • Repeat washing the sore, the antibiotic ointment and the Band-Aid 4 times per day until healed.

  6. Expected Course: Most insect bites itch or hurt for 1 to 2 days. The swelling may last a week.

  7. Call Your Doctor If:

    • Severe pain persists more than 2 hours after pain medicine

    • Infected scab doesn't look better after 48 hours of antibiotic ointment.

    • Bite looks infected (redness, red streaks, increased tenderness)

    • You become worse

Infected Sore or Scab

  1. Reassurance:

    • Sometimes a small infected sore can develop at the site of a cut, scratch, insect bite, or sting.

    • The typical appearance is a sore smaller than 1 inch (2.5 cm) in diameter. It is often covered by a soft, 'honey-yellow' or yellow-brown crust or scab. Sometimes the scab may drain a tiny amount pus or yellow fluid. Usually there is minimal to no pain.

    • Small infected sores usually gets better with regular cleansing and use of an antibiotic ointment.

  2. Cleaning:

    • Wash the area 2-3 times daily antibacterial soap and warm water.

    • Gently remove any scab. The bacteria live underneath the scab. You may need soak the scab off by placing a warm wet washcloth (or gauze) on the sore for 10 minutes.

  3. Antbiotic Ointment:

    • Apply an antibiotic ointment 3 times per day.

    • Cover the sore with a Band-Aid to prevent scratching and spread.

    • Use Bacitracin ointment (OTC in U.S.) or Polysporin ointment (OTC in Canada) or one that you already have.

  4. Avoid Picking: Avoid scratching and picking. This can worsen and spread a skin infection.

  5. Contagiousness:

    • Infected sores can be contagious by skin to skin contact.

    • Wash your hands frequently and avoid touching the sore.

    • Work and School: You can attend school or work if it is covered.

    • Contact Sports: Generally, you need to receive antibiotic treatment for 3 days before you can return to the sport. There can be no pus or drainage. You should check with your trainer, if there is one for your sports team.

  6. Expected Course:

    • The sore should stop growing in 1 to 2 days and it should begin improving within 2-3 days.

    • The sore should be completely healed in 7-10 days.

Preventing Insect Bites

  1. Prevention:

    • Wear long pants and long-sleeved shirts.

    • Avoid being outside when the insect is most active. Many insects that cause itchy bites are most active at sunrise or sunset (e.g., Chiggers, No-See-Ums, Mosquitoes).

    • Insect repellents containing DEET are effective in preventing many itchy insect bites.

  2. DEET - An Insect Repellent

    • DEET is a very effective insect repellent. It also repels ticks.

    • Higher concentrations of DEET do work better - but there appears to be no benefit in using DEET concentrations above 50%. For children and adolescents, the American Academy of Pediatrics recommends a maximum concentration of 30%. Health Canada recommends using a concentration of 5-30% for adults.

    • Apply to exposed areas of skin. Do not apply to eyes, mouth or irritated areas of skin. Do not apply to skin that is covered by clothing.

    • Remember to wash it off with soap and water when you return indoors.

    • DEET can damage clothing made of synthetic fibers, plastics (e.g., eye glasses), and leather.

    • Breastfeeding women may use DEET. No problems have been reported (CDC 2003).

    • Read the label carefully.

  3. Picaridin (also called KBR 3023):

    • In 2005 the CDC added Picaridin to its list of recommended insect repellents.

    • Evidence indicates that it works just as well as DEET.

    • It has been used in other countries for years, including Europe, Australia, Latin America and Asia.

    • Read the label carefully.

West Nile Virus Information

  1. Symptoms of WNV:

    • No clinical symptoms: 80% of infections.

    • Mild febrile illness: 20% of infections. Symptoms include fever, headache, body aches, and occasionally a skin rash. These symptoms last 3-6 days and resolve without any treatment (also called WNV fever).

    • Encephalitis or viral meningitis: 0.7% (1 in 150 people) of infections. Symptoms are obvious: high fever, stiff neck, confusion, coma, convulsions, muscle weakness or paralysis. The muscle weakness is often unilateral.

    • Fatal outcome: 10% of those hospitalized

    • Pediatric cases are generally mild. Most deaths and encephalitis occur in people over age 60.

  2. Diagnosis of WNV:

    • Mild cases do not need to be diagnosed.

    • Severe cases (with encephalitis and viral meningitis) would all be hospitalized based upon their symptoms, and the disease would be diagnosed by tests on the blood and spinal fluid. These tests are not available for the usual mild infections seen with this virus.

  3. Treatment of WNV:

    • No special treatment is needed after a mosquito bite.

    • There is no specific treatment or anti-viral agent for West Nile virus.

    • Patients who require admission are treated supportively with IV fluids, airway management and good nursing care.

    • There is no vaccine available to prevent West Nile Virus in humans.

  4. WNV - Spread by Mosquito:

    • The West Nile virus is spread by the bite of a mosquito. The reservoir for the virus is infected birds.

    • Even in an area where West Nile virus has been identified, less than 1% of mosquitoes carry the virus.

    • Transmission is mosquito-to-human.

    • Person-to-person spread does not occur (eg, from kissing, touching, sharing glassware, or sexual intercourse.)

    • Mothers with mosquito bites can continue breast-feeding (CDC 2003).

    • Incubation period: 3-14 days after the mosquito bite.

  5. Call Your Doctor If:

    • Fever occurs

    • Spreading redness or a red streak occurs

    • Sore increases in size

    • Sore not improving after 2 days using antibiotic ointment

    • Sore not completely healed in 7 days (1 week)

    • New sore appears

    • You become worse

And remember, contact your doctor if you develop any of the "Call Your Doctor" symptoms.

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