It’s a natural for a mosquito bite to turn into a blister for some people. But if you also notice symptoms of infection or an allergic reaction, you should seek a doctor.

Mosquito bites are itchy bumps that occur after female mosquitoes puncture your skin to feed on your blood, which helps them produce eggs. When they feed, they inject saliva into your skin. Proteins in the saliva cause a mild immunologic reaction, which is what leads to the bump and itchiness.

These bumps are usually puffy, red or pink, and appear a few minutes after you get bitten. However, some people may have a more severe reaction, which can lead to fluid-filled blisters instead of puffy bumps.

Read on to learn more about why this happens and how to treat a mosquito bite that turns into a blister.

Some people have stronger reactions than others to mosquito bites. This reaction can include a lot of swelling, beyond the small bump most people get. When the area becomes swollen, fluid can come up under the top layers of skin and form a blister.

This reaction is natural. While everyone has a mild reaction to mosquito bites, some people are more likely to have quicker reactions than others. There’s nothing you can do or not do to prevent a blister from forming when you get a mosquito bite.

However, children, people with immune system disorders, and people who are bitten by a type of mosquito they haven’t previously been exposed to may have more serious reactions.

In the case of children, this may be because they aren’t desensitized to a mosquito’s saliva like most adults are.

Mosquito bites, including ones that blister, will usually go away by themselves in a few days to a week. Until they do, you can relieve some of your symptoms.

Protecting the mosquito bite blister is important. When the blister first forms, gently clean it with soap and water, then cover it with a bandage and petroleum jelly, like Vaseline. Don’t break the blister.

If the blister is itchy, you can apply lotion before covering it. If the lotion doesn’t work, you can take an oral antihistamine.

See a doctor if you have signs of:

  • Infection. Pus, sores, fever, and redness that spreads from the bite site and doesn’t go away can be symptoms of infection, as well as swelling in your lymph nodes.
  • Mosquito-borne diseases. For example, West Nile virus symptoms include headache, joint pain, fever, fatigue, and a general feeling of being unwell.
  • Allergic reaction. This may be a medical emergency.
Medical emergency

It’s possible to have a serious allergic reaction after being bitten by a mosquito. Go to the nearest emergency room if you have a blister and the following symptoms:

Common symptoms of a mosquito bite include:

  • itchiness
  • puffy red or pink bump, or multiple bumps, that appear a few minutes after the bite
  • dark spot once it heals

Some people may have more serious reactions to mosquito bites. These can include:

  • a lot of swelling and redness
  • low-grade fever
  • swollen lymph nodes
  • hives
  • swelling in areas away from bite, like your joints, face, or tongue
  • dizziness
  • trouble breathing (a sign of anaphylaxis that needs emergency medical attention)

Most bug bites will just create a small bump and itch for a few days. However, there are other types of bug bites that can blister, including:

See a doctor immediately if you think you might have been bitten by a brown recluse spider. These bites can cause a serious reaction.

It might be impossible to totally avoid mosquito bites, but there are some ways you can reduce your risk for getting bitten. Follow these tips:

  • Wear long pants and long sleeves while outside.
  • Avoid outdoor activities between dusk and dawn, when mosquitoes are most active.
  • Use insect repellent with DEET, icaridin, or oil of lemon eucalyptus. Be sure to follow the product’s directions. Be careful not to get them in your eyes or any cuts.
  • Wear a hat that protects your neck and ears.
  • Use mosquito netting if you’re sleeping outdoors.
  • Eliminate standing water near your home, such as in gutters or wading pools. Female mosquitoes lay their eggs in standing water.
  • Keep the doors and windows of your home closed, and make sure screens don’t have any holes.
  • Avoid using heavy perfumes, which may attract mosquitoes.

Most mosquito bites lead to a puffy, itchy bump. However, in some cases, they can turn into blisters.

While this is a more robust reaction, it’s not a sign of a problem unless you have symptoms of an infection or allergic reaction, such as fever or trouble breathing.

See a doctor if you have any symptoms or signs of an allergic reaction or infection.