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Mosquito Bite


  • Bites from a mosquito
  • Cause itchy, red bumps
  • Often they look like a hive
  • West Nile Virus (WNV) questions are also covered

Types of Reactions to Mosquito Bites

  • Red Bumps. In North America, mosquito bites are mainly an annoyance. They cause itchy red skin bumps. Often, the bite looks like hives (either one large one or several small ones).
  • When a mosquito bites, its secretions are injected into the skin. The red bumps are the body's reaction to this process.
  • Suspect mosquito bites if there are bites on other parts of the body. Most bites occur on exposed parts such as face and arms.
  • Swelling. Bites of the upper face can cause severe swelling around the eye. This can last for several days. With bites, the swelling can be pink as well as large (especially age 1-5 years).
  • Disease. Rarely, the mosquito can carry a serious blood-borne disease. In the US and Canada, this is mainly West Nile Virus (WNV). In Africa and South America, they also carry malaria and yellow fever.
  • Prevention. Insect repellents can prevent mosquito bites. Use DEET (applied to skin) and permethrin (applied to clothing).

Cause of Mosquito Bite Reaction

  • The skin bumps are the body's reaction to the mosquito's saliva.
  • While it's sucking blood, some of its secretions get mixed in.

Mosquito Life Cycle

  • Only female mosquitoes bite. They need a blood meal to produce eggs. The female may bite 20 times before she finds a small blood vessel. She then sips blood for 90 seconds.
  • Males eat flower nectar and plant juices.
  • 170 species of mosquito are in North America.
  • At a far distance, they are attracted by smell (breath odors, sweat and perfumes). They can smell up to 120 feet (36 meters). At a close distance, they are attracted by body heat and movement.

Risk Factors for Increased Mosquito Bites

  • Warmer body temperature
  • Male more than female
  • Children more than adults
  • Breath odors
  • Sweating
  • Perfumed soaps and shampoos

Complications of Insect Bites

  • Impetigo. A local bacterial infection. Gives sores, soft scabs and pus. Caused by scratching or picking at the bites. More common in itchy bites.
  • Cellulitis. The bacterial infection spreads into the skin. Gives redness spreading out from the bite. The red area is painful to the touch.
  • Lymphangitis. The bacterial infection spreads up the lymph channels. Gives a red line that goes up the arm or leg. More serious because the infection can get into the bloodstream. This is called sepsis.

When To Call

Call 911 Now

  • Life-threatening allergic reaction suspected. Symptoms include sudden onset of trouble breathing or swallowing.
  • Can't wake up
  • You think your child has a life-threatening emergency

Go to ER Now

  • Hard to wake up
  • Acts or talks confused
  • Can't walk or can barely walk
  • Stiff neck (can't move neck normally)

Call Doctor or Seek Care Now

  • Spreading red area or streak with fever
  • Your child looks or acts very sick
  • You think your child needs to be seen, and the problem is urgent

Contact Doctor Within 24 Hours

  • Painful spreading redness started more than 48 hours after the bite. Note: any redness starting in the first 24 hours is always a reaction to the bite.
  • More than 72 hours since the bite and redness gets larger
  • Unexplained fever and recent travel outside the country to high risk area
  • You think your child needs to be seen, but the problem is not urgent

Contact Doctor During Office Hours

  • Pregnant and recently traveled to or lives in a place with a Zika outbreak
  • Scab that looks infected (drains pus or gets bigger) not better with antibiotic ointment
  • Severe itching not better after 24 hours of using steroid cream
  • You have other questions or concerns

Self Care at Home

  • Normal mosquito bite
  • Questions about West Nile Virus
  • Questions about insect repellents (such as DEET)

Care Advice

Treatment for Mosquito Bites

What You Should Know About Mosquito Bites:

  • In the United States and Canada, mosquito bites rarely carry any disease.
  • They cause itchy red skin bumps.
  • Most of the time, the bumps are less than ½ inch (12 mm) in size. In young children, they can be larger. See Large Local Reactions, below.
  • Some even have small water blisters in the center.
  • A large hive at the bite does not mean your child has an allergy.
  • These are normal reactions.
  • Here is some care advice that should help.

Large Local Reactions:

  • Some people react more to mosquito bites than others do. This is very common in young children.
  • In these children, the redness can be large (2-4 inches or 5-10 cm). This redness starts right after the bite. It may keep getting larger for 2 to 3 days. This is still normal.
  • It is a harmless, local allergic reaction to the mosquito saliva (spit). It is not related to a severe allergic reaction (anaphylaxis).
  • It also is not a sign of infection. Infections of mosquito bites are painful to touch. They are also not common. They most often occur in bites that children have scratched or picked at. Most start with an infected sore or scab.

Steroid Cream for Itching:

  • To reduce the itching, use 1% hydrocortisone cream (such as Cortaid). No prescription is needed. Put it on 3 times a day until the itch is gone. If you don't have, use a baking soda paste until you can get some.
  • If neither is available, use ice in a wet washcloth for 20 minutes.
  • Also, you can put firm, sharp, direct, steady pressure on the bite. Do this for 10 seconds to reduce the itch. A fingernail, pen cap, or other object can be used.

Allergy Medicine for Itching:

  • If itching becomes severe, give a dose of Benadryl or other allergy medicine.
  • No prescription is needed. Age limit for Benadryl: 1 and older.
  • If Benadryl is needed for more than a few days, switch to a long-acting allergy medicine (such as Zyrtec). Age limit: 6 months and older.
    • Zyrtec dosing for 6 months to 2 years: 2.5 mL (2.5 mg) every 24 hours.
    • Zyrtec dosing for 2 years and older: follow package directions.

Try Not to Scratch:

  • Cut the fingernails short.
  • Help your child not to scratch.
  • Reason: prevent a skin infection at the bite site.

Antibiotic Ointment:

  • If the bite has a scab and looks infected, use an antibiotic ointment. An example is Polysporin.
  • No prescription is needed. Use 3 times per day. Note: usually infection caused by scratching bites with dirty fingers.
  • Cover the scab with a bandage. This will help prevent scratching and spread.
  • Wash the sore and use the antibiotic ointment 3 times per day. Do this until healed.

What to Expect:

  • Most mosquito bites itch for 3 or 4 days.
  • Any pinkness or redness lasts 3 or 4 days.
  • The swelling may last 7 days.
  • Bites of the upper face can cause severe swelling around the eye. This does not hurt the vision and is harmless.
  • The swelling is often worse in the morning after lying down all night. It will improve after standing for a few hours.

Call Your Doctor If:

  • Bite looks infected. Redness gets larger after 48 hours or pus discharge.
  • Bite becomes very painful
  • You think your child needs to be seen
  • Your child becomes worse

West Nile Virus Questions

West Nile Virus (WNV) - What You Should Know:

  • WNV is a disease carried by mosquitoes. It can be spread to humans through a mosquito bite.
  • About 1% of mosquitoes carry WNV.
  • Of people who get WNV, less than 1% get the serious kind.
  • Here are some facts that should help.

Symptoms of WNV:

  • No symptoms: 80% of WNV infections.
  • Mild symptoms: 20% of infections. Symptoms include fever, headache, and body aches. Some have a skin rash. These symptoms last 3-6 days. They go away without any treatment. This is called WNV fever.
  • Serious symptoms: less than 1% (1 out of 150) of WNV infections. Symptoms are high fever, stiff neck, confusion, coma, seizures, and muscle weakness. The muscle weakness is often just on one side. The cause is infection of the brain (encephalitis) or spinal cord (viral meningitis).
  • Death: 10% of those who need to be in the hospital.
  • Child cases are most often mild. Most serious cases occur in people over age 60.

Diagnosis of WNV:

  • Mild symptom cases do not need to see a doctor. They do not need any special tests.
  • Severe symptom cases (with encephalitis or viral meningitis) need to see a doctor right away. Special tests on the blood and spinal fluid will be done to confirm WNV.
  • Pregnant or nursing women need to see a doctor if they have WNV symptoms.

Treatment of WNV:

  • No special treatment is needed after a mosquito bite.
  • There is no special treatment or anti-viral drug for WNV symptoms.
  • People with serious symptoms often need to be in the hospital. They will be given IV fluids and airway support.
  • There is not yet a vaccine to prevent WNV in humans.

WNV - Spread by Mosquitoes:

  • WNV is spread by the bite of a mosquito. The mosquito gets the virus from biting infected birds.
  • Even in an area where WNV occurs, less than 1% of mosquitoes carry the virus.
  • Spread is mosquito-to-human.
  • Person-to-person spread does not occur. Kissing, touching, or sharing a glass with a person who has WNV is safe.
  • Mothers with mosquito bites can breastfeed (CDC 2003), unless they get symptoms of WNV.
  • It takes 3-14 days after the mosquito bite to get WNV.
  • In United States and Canada, the peak summers for WNV were 2002, 2003 and 2012.

Insect Repellent Questions

Prevention Tips:

  • Wear long pants, a long-sleeved shirt and a hat.
  • Avoid being outside when the bugs are most active. Mosquitoes are most active at dawn and dusk. Limit your child's outdoor play during these times.
  • Get rid of any standing water. Reason: it's where they lay their eggs.
  • Keep bugs out of your home by fixing any broken screens.
  • Insect repellents containing DEET are very good at preventing mosquito bites. Read the label carefully.

DEET Products - Use on the Skin:

  • DEET is a good mosquito repellent. It also repels ticks and other bugs.
  • U.S. Age limit: none. You can use DEET products on all children (AAP).
  • U.S.: for newborns to 2 years old, use 10% DEET. After 2 years old, can use 30% DEET.
  • Protection: 10% DEET protects for 2 hours. 30% DEET protects for 6 hours.
  • Don't put DEET on the hands if your child sucks their thumb or fingers. Reason: prevent swallowing DEET.
  • Warn older children who apply their own DEET to use less. A total of 3 or 4 drops can protect the whole body.
  • Put on exposed areas of skin. Do not use near eyes or mouth. Don't use on skin that is covered by clothing. Don't put DEET on sunburns or rashes. Reason: DEET can be easily absorbed in these areas.
  • Wash it off with soap and water when your child comes indoors.
  • Caution: DEET can damage clothing made of man-made fibers. It can also damage plastics (eye glasses) and leather. DEET can be used on cotton clothing.

Permethrin Product - Use on Clothing:

  • Products that contain permethrin (such as Duranon) work well to repel mosquitos and ticks.
  • Unlike DEET, these products are put on clothing instead of on the skin.
  • Put it on shirt cuffs, pant cuffs, shoes and hats. Can also put it on mosquito nets and sleeping bags.
  • Do not put permethrin on the skin. Reason: sweat changes it so it does not work.

Picaridin Products:

  • Picaridin is a repellent that is equal to 10% DEET.
  • It can safely be put on skin or clothing.



Female Mosquito

The photo shows a female mosquito feeding on a person.

Source: CDC PHIL
From the CDC's Public Health Image Library (, ID#1863, in the public domain. Photo credit: James Gathany.

Barton Schmitt MD, FAAP
Disclaimer: this health information is for educational purposes only. You, the reader, assume full responsibility for how you choose to use it.
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