Why Mosquito Bites Itch, and How to Stop It

Written by Shiv Sudhakar, MD | Reviewed by Patricia Pinto-Garcia, MD, MPHPublished on May 2, 2022

Key takeaways:

• Mosquito bites are itchy because of histamine your immune system releases. 
• You can stop mosquito bite itching with anti-itching remedies like over-the-counter medications and oatmeal baths.
• Scratching mosquito bites can lead to skin infections, so try to avoid scratching mosquito bites.

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Most people are familiar with the annoying reality of mosquito bites. Sometimes, no matter how careful you are, you end up with multiple, itchy bites. 

While you can’t completely avoid mosquitoes, there’s still plenty you can do to relieve itchy mosquito bites. Let’s take a look at why mosquito bites itch — and what you can do to stop mosquito bites from itching. 

Why do mosquito bites itch?

A mosquito injects saliva into your body when it bites you. This triggers your immune system to release histamine, and a side effect of this substance is itchy skin. 

Histamine is a signal to the rest of the immune system that there’s something in the body that shouldn’t be there. This signal alerts the immune system to work on getting rid of the mosquito saliva. 

Mosquito bite itching usually starts about 20 minutes after a bite and gets worse over the next 24 to 36 hours. The itching will gradually disappear over 7 to 10 days.

Why is my mosquito bite so big?

Some people develop bigger bumps after mosquito bites. The itchy, red welt that’s left behind after a mosquito bite is actually an urticarial reaction, or a hive. So people who develop these hives are actually having an allergic reaction to mosquito bites. 

Just like with other types of allergic reactions, some people react more severely than others. A larger hive is a sign that your immune system is reacting more strongly to the mosquito’s saliva.

Some people don’t react to mosquito bites at all, while others react so severely that they develop anaphylaxis, a life-threatening allergic reaction. 

Other people develop very large local reactions. These reactions aren’t just itchy — they’re also painful and can form blisters. If you develop large, painful welts after getting bit by mosquitoes, you may have this type of reaction, also called Skeeter’s syndrome. 

How can you get mosquito bites to stop itching?

There are several things you can try at home to stop a mosquito bite from itching:

• Ice packs: Ice can help decrease swelling and itchiness. Apply an ice pack to your bite for about 10 minutes. You can reapply whenever the itching gets worse. Make sure to wrap the ice pack (or ice) in a towel. Applying ice directly to your skin can lead to skin damage. 
• Anti-itch pastes: Try some DIY anti-itch pastes. Mix 1 tablespoon of baking soda with enough water to create a paste. Or mix oatmeal bath products with water to form a paste. Apply your paste of choice to your bite for 10 minutes and then wash it off. You can reapply the paste for worsening itchiness as you need it. 
• Steroid cream: You can try anti-itch cream for mosquito bites to help relieve itching. Over-the-counter (OTC) 1% hydrocortisone cream is a great option. Make sure you stop using it after a few days to avoid side effects like skin discoloration. 
• Antihistamines: OTC antihistamine medications can also relieve mosquito bite itching. You can try loratadine (Claritin) or diphenhydramine (Benadryl) — just make sure to follow directions for dosing. 

When should I see a doctor about my mosquito bite?

Avoiding infection is the most important reason to resist the urge to scratch mosquito bites. Scratching causes breaks in the skin. These breaks let bacteria get into the skin and cause infections, like cellulitis or impetigo.

If you have signs of a skin infection, you should see a healthcare provider right away. These signs include:

• Fever
• Worsening redness, tenderness, or pain of your mosquito bite
• Red streaking that moves away from the bite toward your heart
• Blisters or yellow crusting at the bite 
• Pus, oozing, or other drainage from the bite

How can I prevent mosquito bites?

Dealing with mosquito bites isn’t fun. So the best option is to avoid getting bit in the first place. Here are some things you can try: 

• Use EPA-approved insect repellent that repels mosquitoes. 
• Cover up as much skin as possible when you’re outdoors. Wear long sleeves and pants outdoors if you can.
• Avoid areas where there are lots of mosquitoes, if possible.

You can also help lower the number of mosquitos in your area by removing sources of standing water. Mosquitoes can lay thousands of eggs in very small amounts of water. Make sure to empty containers that can collect water at least once a week. Don’t forget small items like pet bowls, vases, and flower pots. 

The bottom line

A mosquito bite triggers the immune system to release histamine, which causes the familiar itchy bumps. Scratching mosquito bites can lead to skin infection. Simple home remedies, over-the-counter antihistamines, and steroid creams can help soothe the urge to itch. 

Some people have more severe reactions to mosquito bites. But most of the time bites get better and go away after about a week. You can prevent mosquitoes from biting you by using EPA-approved insect repellent, wearing long-sleeve clothing, and avoiding places where there are lots of mosquitoes.