Overview

Mosquito bites are the itchy bumps that form on the skin after mosquitoes feed on your blood. The bumps usually go away without treatment in a few days. Some mosquito bites may get very swollen, sore and inflamed. This type of reaction, sometimes called skeeter syndrome, is most common in children.

Mosquito bites can cause severe illnesses if the insects carry certain viruses or parasites. Infected mosquitoes can spread West Nile virus, Zika virus, and the viruses that cause malaria, yellow fever and some types of brain infection.

Symptoms

Mosquito bites often happen on parts of the body that aren't covered by clothing. Symptoms include:

  • An itchy, inflamed bump that forms a few minutes after a bite
  • A painful spot that looks like a hive and forms within 24 hours after a bite
  • Small blisters

A severe reaction to mosquito bites can cause:

  • A large, swollen, inflamed area
  • A hive-like rash
  • Swelling around the eyes

Children are more likely to have a severe reaction than are adults.

When to see a doctor

Contact your health care provider if the mosquito bites seem to occur with warning signs of a serious condition. These might include a high fever, severe headache, body aches and signs of infection.

Causes

Mosquito bites are caused by female mosquitoes feeding on your blood. As a biting mosquito fills itself with blood, it injects saliva into your skin. The saliva triggers an immune system reaction that results in the classic itching and bump.

Mosquitoes are attracted to smells, such as from sweat, floral scents and exhaled carbon dioxide.

Risk factors

Risk factors for mosquito bites include:

  • Sweating
  • Wearing floral scents
  • Living in an area where mosquitoes are active
  • Spending time outside without using mosquito repellent

Complications

Scratching bites can lead to infection.

Mosquitoes can carry the viruses that cause certain diseases, such as West Nile virus and the viruses that cause malaria, yellow fever and dengue fever. The mosquito gets a virus or parasite by biting an infected person or animal. Then when it's biting you, the mosquito can transfer that virus or parasite to you through its saliva. West Nile, dengue fever and some types of encephalitis occur in the United States. Other diseases, such as malaria and yellow fever, are far more common in tropical areas of the world.

Prevention

Mosquitos bite during both day and night, and they can live indoors. You can take several steps to protect yourself from mosquito bites.

Avoid and exclude mosquitoes

Limit exposure to mosquitoes by:

  • Repairing any tears in the screens on windows, doors and camping gear
  • Using mosquito netting over strollers and cribs
  • Using mosquito netting when sleeping outdoors
  • Selecting self-care products that don't have scents

Use insect repellent

Use insect repellent when mosquitoes are active. The most effective insect repellents in the United States include one of these active ingredients:

  • DEET
  • Icaridin, also called picaridin
  • Oil of lemon eucalyptus
  • IR3535
  • Para-menthane-diol (PMD)
  • 2-Undecanone

These ingredients temporarily repel mosquitoes and ticks. DEET may offer longer lasting protection. Whichever product you choose, read the label before you apply it. If you're using a spray repellent, apply it outdoors and away from food. You may need to reapply it 6 to 8 hours later if you're still in an area where mosquitoes are active.

If you're also using sunscreen, put it on first, about 20 minutes before applying the repellent. Avoid products that have both sunscreen and repellent, because you'll likely need to reapply sunscreen more often than repellent. And it's best to use only as much repellent as you need and to wash your hands after applying it.

Used according to package directions, these products are generally safe for children and adults, with a few exceptions:

  • Don't use DEET-containing products on infants younger than 2 months.
  • Don't use icaridin on infants younger than 6 months.
  • Check the labels of products with oil of lemon eucalyptus — some aren't suitable for children under 3 years old.
  • Don't use para-menthane-diol on children under 3 years old.
  • Don't let young children get insect repellent on their hands, as they might get it in their mouths.
  • Don't apply repellent near the eyes and mouth.
  • Don't apply repellent under clothing.
  • Don't apply repellent over sunburns, cuts, wounds or rashes.
  • When the risk of mosquito bites has passed, wash repellent off the skin with soap and water.

Treat clothing and outdoor gear

Permethrin is an insecticide and insect repellent used for added protection. This product is made to use on clothing and outdoor gear, not skin. Check the product label for instructions. Some sporting goods stores sell clothing pretreated with permethrin. Don't wash bed nets or set them in sunlight, as this breaks down permethrin. Clothing sprayed with permethrin can offer protection for two washings and up to two weeks.

Use protective clothing and gear

Weather permitting, wear a hat, long-sleeved shirts and long pants.

Take preventive medicine

Get vaccinations or take preventive medicine that your health care provider has suggested.

Think about whether you tend to have large or severe reactions to mosquito bites — skeeter syndrome. You might want to take a nondrowsy, nonprescription antihistamine when you know you'll be exposed to mosquitoes.

Reduce mosquitoes around your home

Get rid of standing water, which mosquitoes need to breed. Take these steps to keep your house and yard free of mosquito pools:

  • Unclog roof gutters.
  • Empty children's wading pools at least once a week, and preferably more often.
  • Change water in birdbaths at least weekly.
  • Get rid of old tires in your yard.
  • Empty outdoor flower pots regularly or store them upside down so that they can't collect water.
  • Drain your fire pit if water collects there.
By Mayo Clinic Staff