Mosquito Bites Affect Each Person Differently—It All Depends on Your Immune System

Mosquito Bites Affect Each Person Differently—It All Depends on Your Immune System

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You probably do your best to avoid getting bitten by mosquitos, but mosquito bites can and do happen regularly in the warmer months. Cue you, reaching for anti-itch cream, and wondering “why do mosquito bites itch, anyway?”

For what it’s worth, not everyone gets mosquito bites that itch—but it’s very, very common to feel the urge to scratch after you’ve been bitten. So, what’s going on here, exactly? Bug experts and an allergist break it all down.

What happens when a mosquito bites you?

To understand why mosquito bites itch, it’s important to first get into the details of what happens when a mosquito bites you.

Female mosquitoes need to eat blood in order to get certain nutrients to develop eggs, explains Thomas Dobrinska, a board-certified entomologist with Ehrlich Pest Control. (It’s worth pointing out, per Ben Hottel, technical services manager at Orkin, that male mosquitos don’t feed on blood. Instead, they eat nectar.)

A female mosquito has five needle-like structures that make up her mouthparts, Dobrinska says: Four of them are designed to draw blood, while one functions as a pump for saliva.

“The saliva contains enzymes and anticoagulants that facilitate the uptake of the blood as well as anesthetic substances which reduces the pain of the bite and prevents a defensive reaction from the host,” Dobrinska says. After puncturing your skin with their mouthparts and feeding on your blood, “mosquitoes leave hard, itchy bumps” in their wake, Hottel says.

OK, so why do mosquito bites itch?

The actual bumps that are caused by the mosquito bite “are caused by an immune response to mosquito saliva,” says Kara Wada, M.D., an allergist and immunologist at The Ohio State University Wexner Medical Center.

Not everyone has the same reaction to mosquito bites, though—some may get really itchy while others may just have a minor urge to scratch. “Some people will develop more significant reactions called large local reactions—sometimes termed ‘Skeeter Syndrome,’” Dr. Wada says. “These reactions involve a more robust immune system response that causes increased swelling and redness that can last longer than run-of-the-mill bite reactions.”

True allergies to mosquito bites are rare, Dr. Wada says, but some people who are allergic to mosquito saliva may have hives and even anaphylaxis, a severe and life-threatening allergic reaction that can cause swelling and difficulty breathing.

How can you get relief from itchy mosquito bites?

You’ve probably heard that scratching can make things worse, and that’s actually true. “Scratching can make the itching and swelling worse by trigging more inflammation and by opening up the skin to potential infection,” Dr. Wada says.

If you’ve been bitten and you’re itchy, Dr. Wada says you have a few potential options for relief:

  • Use over-the-counter long-acting antihistamines like loratadine, cetirizine, or fexofenadine

  • Put a topical steroid cream on the bite site

  • Talk to your doctor about a prescription strength steroid cream (if the reaction is intense)

How can you prevent mosquito bites?

The best way to avoid having itchiness from mosquito bites is to do your best to prevent the bites in the first place.

Hottel recommends doing the following to protect yourself:

  • Wear light-colored, loose fitting, long pants and long-sleeved shirts to help prevent the female mosquito’s mouthparts from piercing into your skin.

  • Be more proactive by making yourself “repulsive” to mosquitoes by wearing insect repellent. The Centers for Disease Control and Prevention (CDC) recommends using only products approved by the Environmental Protection Agency (EPA) that contain either DEET, Picaridin, IR3535, Oil of lemon eucalyptus, Para-menthane-diol or 2-Undecanone.

You can also do a few things around your home and yard to stay safe, Dobrinska says:

  • Ensure your screens and window frames are in good condition

  • Clean your rain gutters so they’re free of debris and polluted water where mosquitos can breed

  • Keep your grass cut low and trim vegetation that may be protecting adult mosquitoes

  • Overturn any potential water-collecting containers like trash bins, tires, and plastic pools

  • Drain pool covers that may harbor standing water

  • Change water in birdbaths and pet waterers at least once a week

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