Why do mosquito bites itch and swell up?
When a mosquito bites, our immune system kicks in to protect us against the attack. This is similar to an allergic reaction and causes a raised, itchy bump to appear.
This article discusses what makes mosquito bites itch and swell, and what treatments are available.
Why do mosquito bites itch?
Mosquito bites itch and swell because of the body's histamine response.
When a mosquito bite breaks the skin, a person's body recognizes the mosquito's saliva as a foreign substance. This causes an immune system response, which aims to flush out the intruder.
The swelling around the bite is caused by histamine, which is produced by the immune system.
Histamine increases blood flow and white blood cell count around the affected area, which causes inflammation or swelling.
Mosquito bites itch because histamine also sends a signal to the nerves around the bite.
The first time a person is bitten, their body may not react in this way. The immune response is something that the body learns after being exposed to a foreign substance.
Some people may never react to a bite. Others might become more tolerant to a mosquito's saliva over time. For many, the reaction remains consistent, and mosquito bites continue to be an annoyance.
Why do mosquitoes bite us?
Mosquitoes bite humans to drink their blood. The nutrients contained in a human's blood help female mosquitoes to make the eggs they need to reproduce. Only female mosquitoes bite people.
A mosquito uses the sharp tip of its straw-like mouth (proboscis) to pierce a person's skin. It locates the blood vessel and draws blood up through its mouth.
As it does this, it injects saliva that contains an anticoagulant. This stops the person's blood from clotting. If the blood were to clot around the mosquito's mouth, it might get stuck.
Does scratching make it worse?
Scratching mosquito bites may make the itching worse.
Mosquito bites itch due to inflammation. Rather than relieving the itching, scratching an already inflamed area increases inflammation. This makes the area even itchier.
Scratching may also increase the risk of infection if it breaks the skin. If the area becomes infected, it will be much itchier and will take longer to heal.
Applying aloe vera to mosquito bites may help healing and reduce itching.
The following treatments may help to reduce the swelling and itching of a mosquito bite:
Antihistamines are an over-the-counter medication that help to reduce inflammation and itching. They are an effective way to treat mosquito bites.
Applying heat to a mosquito bite may help reduce the inflammation and itching.
A 2011 study found that locally administered heat brought fast relief to mosquito bite symptoms.
Honey is antibacterial and may help wounds heal. A 2011 study found that natural honey can reduce inflammation and prevent infection.
For this reason, natural honey may help reduce the symptoms of a mosquito bite when applied to the affected area. It is essential to wash it off before going outside, as it can attract mosquitoes and other insects.
Corticosteroid creams can reduce inflammation and itching.
As these creams are steroid based, people should use them sparingly and should not apply them to open wounds. They may also cause the skin to thin with repeated use.
One species of aloe, Aloe littoralis, has been shown to reduce inflammation and encourage wound healing in animal studies.
Applying aloe gel to a mosquito bite may help relieve the inflammation and soothe the itching.
The anti-inflammatory properties of basil oil suggest it could help to relieve mosquito bite inflammation.
When to see a doctor
Mosquito bites may cause swollen joints, hives, and high fever in some people.
Mosquito bites can become infected, which may mean they take longer to heal. It is a good idea for a person to speak to a doctor about any suspected infections.
Some people are very allergic to mosquito bites. For these people, being bitten may cause an anaphylactic shock. Symptoms of this include:
- trouble breathing
- facial swelling
If a person has an anaphylactic shock, they need emergency medical treatment, usually an injection of epinephrine through an EpiPen.
Mosquito bites may also cause the following symptoms in some people:
- high fever
- swollen joints
A person should speak to a doctor if they experience these symptoms. A doctor will typically recommend over-the-counter antihistamines to treat these symptoms in the first instance.
The risk of getting a disease from a mosquito in the United States is low.
If a person is traveling to a country where mosquitoes may be carrying disease, they should speak to their doctor for advice. A doctor can advise the best way to stay safe and reduce the risk of infection.
To reduce the risk of being bitten by mosquitoes, a person should:
- use mosquito repellent
- wear long-sleeved tops and long trousers
- wash frequently, as sweat may attract mosquitoes
- avoid alcohol, as this can increase probability of being bitten
Mosquito bites usually heal within a few days. Avoid scratching the bite when it itches to reduce healing time.
If a person has sensitive skin, they may experience some changes in skin pigmentation around the bite as it heals. Using creams that contain vitamin E and applying sunscreen can help to prevent this.