Why Mosquito Bites Swell, and Why Mosquitoes Bite Some People More
One person at the cookout ends up covered in welts while the person beside them barely gets touched. This article covers why mosquito bites itch, why some swell so much, why mosquitoes pick some people over others, and what calms a bite at home.
- Only female mosquitoes bite. They need the blood to make eggs.
- The itch and the bump come from your body reacting to mosquito saliva.
- A very swollen, sore, inflamed bite can be an allergic reaction called skeeter syndrome.
- People who are mosquito magnets carry more of certain skin acids, and stay magnets for years.
- Most bites heal on their own in a few days. Fever or severe headache needs a doctor.
Why do mosquito bites itch?
Mosquito bites itch because of the mosquito’s saliva. The Mayo Clinic says that as a female mosquito fills with blood, it injects saliva into your skin, and the saliva triggers an immune system reaction that causes the classic itching and bump. Most bites stop itching and heal on their own in a few days.
Only the female bites. The Environmental Protection Agency says only the female mosquito feeds on the blood of people and other animals, and Texas A&M AgriLife explains why: males feed only on nectar, and females need blood to produce eggs.
The Mayo Clinic’s health library entry on mosquito bites describes the usual pattern. An itchy, inflamed bump forms a few minutes after the bite, a painful spot that looks like a hive can follow within 24 hours, and some people get small blisters. Bites often land on skin that clothing does not cover. Scratching is the part to avoid, because the Mayo Clinic says it can lead to infection.
Bitten in bed overnight with no mosquito in sight? The Texas Department of State Health Services says mosquitoes bite day and night and live indoors as well as out, so a mosquito can do it. If the bites keep coming night after night, though, our article on how to tell if you have bed bugs covers the signs to check for.
Why do mosquito bites swell so much?
Some people react strongly to the proteins in mosquito saliva. The Mayo Clinic says a severe reaction can cause a large, swollen, inflamed area, a hive-like rash or swelling around the eyes. This allergic reaction, sometimes called skeeter syndrome, is most common in children.
The Mayo Clinic says children are more likely than adults to have a severe reaction. A big, swollen, inflamed bite is sometimes mistaken for a bacterial infection, and there is no simple blood test for a mosquito allergy. A doctor diagnoses it by whether the large areas of swelling and itching came after mosquito bites.
For people who know they swell badly, the Mayo Clinic suggests taking a nondrowsy, nonprescription antihistamine when you know you will be around mosquitoes. Ask your doctor or pharmacist which one, and how much, for a child.
A bite is usually only an itch, but the Texas Department of State Health Services says mosquito bites in Texas are more than an annoyance, because mosquitoes can carry diseases. Call your health care provider if bites come with a high fever, a severe headache, body aches or signs of infection, the warning signs the Mayo Clinic lists.
Why do mosquitoes bite some people more than others?
Part of it is how your skin smells. A study funded by the National Institutes of Health found that people with more carboxylic acids on their skin drew more mosquitoes, and that it stayed true for years. The Mayo Clinic says mosquitoes are drawn to sweat, floral scents and the carbon dioxide you breathe out.
The National Institutes of Health summary of the study, run by researchers at Rockefeller University, describes how it worked. Sixty-four volunteers wore nylon sleeves on their arms for six hours, and the sleeves were tested on Aedes aegypti, the yellow fever mosquito, a species our mosquito control page lists among the three that do almost all of the biting in Collin County.
The skin of the most attractive volunteers was rich in carboxylic acids, a kind of fatty acid, and the levels stayed steady for a year or more. “If they were a mosquito magnet, they remained a mosquito magnet,” one of the researchers said. The study could not prove the acids cause the preference, only that they go with it, and one person with high levels of every acid tested did not attract mosquitoes.
The time of day matters too. Our mosquito control page says bites in broad daylight point to the Asian tiger mosquito, and bites at dusk and after dark point to the southern house mosquito. Texas A&M AgriLife says the day and night feeders can overlap at dawn and dusk, which may be why so many mosquitoes seem to be out then.
How do you treat mosquito bites?
Most bites need only time, and a few home steps ease the itch. The Mayo Clinic suggests calamine lotion or a nonprescription antihistamine or corticosteroid cream, a paste of baking soda and water, an ice cube rubbed on the bite for 30 seconds, or pressure for 10 seconds. Try not to scratch.
The Mayo Clinic says to reapply a cream or the baking soda paste three times a day until the itch is gone. For stronger reactions, it suggests a nonprescription antihistamine taken by mouth that does not cause sleepiness. You will not need a doctor for an ordinary bite, it says, unless a fever or other symptoms follow.
Mosquito bite reactions, from usual to see a doctor
The reactions and warning signs come from the Mayo Clinic’s health library entry on mosquito bites. The home remedies are its general tips for an itchy bite.
| Reaction | What it looks like | What to do |
|---|---|---|
| Usual bite | An itchy, inflamed bump a few minutes after the bite | Leave it alone, it heals in a few days |
| Later spot | A painful spot like a hive within 24 hours, sometimes small blisters | Cream, an ice cube or a baking soda paste |
| Strong reaction | A large, swollen, inflamed area, a hive-like rash or swelling around the eyes | A nondrowsy antihistamine, and ask a doctor |
| Warning signs | High fever, severe headache, body aches or signs of infection | Call your health care provider |
Children are more likely than adults to have the strong reaction, the Mayo Clinic says.
How to get bitten less at home
- Wear a repellent. The Texas Department of State Health Services says repellents registered with the Environmental Protection Agency are proven safe and effective when used as directed, even for pregnant and breastfeeding women. The Mayo Clinic lists deet, picaridin (also called icaridin) and oil of lemon eucalyptus among the active ingredients that work, and says deet may last longest. For children, it says no deet under 2 months and no picaridin under 6 months, and to check oil of lemon eucalyptus labels, since some are not for children under 3.
- Put sunscreen on first. The Mayo Clinic says to apply sunscreen about 20 minutes before the repellent, and to skip products that combine the two.
- Cover up. The Mayo Clinic suggests a hat, long sleeves and long pants, and Texas A&M AgriLife says the tighter the weave of the fabric, the better it protects.
- Keep them outside. Repair torn screens on windows and doors, and keep doors and windows closed or screened, as the Mayo Clinic and the state health department both advise.
- Skip the perfume outdoors. The Mayo Clinic says mosquitoes are drawn to floral scents and suggests self-care products that have no scent.
The other half is the water they breed in. Our article on mosquito season in Texas covers when the breeding starts in Collin County and how often to empty standing water.
How Pest Me Off handles a yard full of mosquitoes
On the first mosquito control visit, Pest Me Off confirms the species, because daytime bites point to the Asian tiger mosquito and after-dark bites to the southern house mosquito. We treat the shaded shrubs, fence lines and spots under decks where adults rest through the heat of the day, and walk the yard to find, drain and flag every breeding site. The Scorched Earth Barrier on the foliage keeps working for 3 to 4 weeks.
Our Skeeter Beater program comes back every 3 weeks, April through October, and pets and kids are back in the yard in 1 to 2 hours, once the treatment dries. The inspection and estimate are free, with same-day service when you call before noon, in McKinney, Plano, Frisco, Allen and across Collin County.
Bitten every time you step outside? Mosquito control across Collin County.
We confirm the species, treat the shade where adults rest and drain the water where they breed. Free inspection and estimate.
