Mosquito bites and allergies

An allergic reaction to mosquito bites is caused by the formation of antibodies to the protein substance in the mosquito's saliva. The allergy worsens the normal symptoms of mosquito bites - i.e. itching, swelling and redness - but can also cause other symptoms.

However, severe reactions to mosquito bites don't have to be due to allergies; the cause may simply be sensitive skin reacting violently to the bite.

In Denmark, reactions to mosquito bites only lead to life-threatening situations in extremely rare cases. When an insect bite leads to severe symptoms, in the vast majority of cases it is a bee or wasp sting.

If you experience severe symptoms after a mosquito bite or suspect you have an allergy to mosquito bites, you should always seek medical attention.

Mosquito bites can trigger allergies in humans, leading to more severe symptoms when bitten

Allergy to mosquito bites exacerbates the normal symptoms of mosquito bites (itching, swelling and redness), but can also cause other symptoms


Symptoms of an allergic reaction

Although some people have few or no symptoms from mosquito bites, most people experience itching, swelling and redness to some extent.

When you have an allergic reaction to mosquito bites, it's because you have formed antibodies to the protein substance in the mosquito's saliva.

Light reactions

In mild allergic reactions to mosquito bites, the symptoms are the same as in non-allergic people, but slightly more severe. Symptoms include:

  • Itchy skin
  • Swelling around the mosquito bite
  • Hives (red rash) around the mosquito bite

Serious reactions

More severe allergic reactions can cause the following symptoms:

  • Large areas of itchy skin
  • Damage to the skin
  • Bruising around the mosquito bite
  • Hives all over the body
  • Swollen lymph nodes
  • Lymphangitis (inflammation of the lymph nodes)
  • Anaphylactic shock (severe reaction that causes tissue swelling, which can block the airways and cause breathing difficulties, among other things)

If you experience any of the symptoms above, or if you suspect an allergy at all, you should seek medical attention. If you experience very severe reactions to mosquito bites - including severe swelling in areas other than the bite site (anaphylactic shock) - you should always seek medical attention immediately.

However, it should be mentioned that severe reactions such as anaphylactic shock only rarely are triggered by mosquito bites. They are more commonly triggered by the stings of other insects such as bees or wasps. This is because bees and wasps inject venom into our bodies as part of a defense response, whereas mosquitoes inject an anticoagulant protein substance as part of a feeding response. However, some people can react violently to both mosquito bites and bee and wasp stings.


Dangerous connectors

Only in very rare cases are mosquito, midge and midge (midge) bites dangerous. However, bites to the mouth, throat and pharynx can be dangerous because the swelling can block our airways, which can stop the supply of oxygen.

You should always seek medical attention if you are stung in one of these areas - even if you are not allergic to mosquito bites or other insect bites.

In addition, you should also seek medical attention if you:

  • experience some of the severe symptoms of allergic reactions (see list above)
  • have been bitten by many mosquitoes at once and have a reaction
  • have been stung and already suffer from a heart condition
  • experience itching in the palms, ears, scalp or other unusual places

It's worth noting that severe reactions to mosquito bites and other insect bites almost always occur very shortly after the bite.


Treating the allergy

Whether you're allergic to the mosquito's protein substance or not, there are only three real treatment options:

  • Products that relieve the symptoms of mosquito bites (like the ones seen on this page)
  • Antihistamines (available over the counter at the pharmacy - talk to your doctor about this)
  • Adrenal cortex hormone (which is prescription-only and available after a check-up with a doctor)

In the vast majority of cases, the first two treatment options provide ample symptom relief.


Allergy test against mosquitoes

In Denmark, it is possible to be tested for mosquito allergy using a blood test (a so-called mosquito allergy test). However, the allergy test is not usually used in practice because:

  • it only tests allergy to 1 species of mosquito (there are more than 30 species of biting mosquitoes in the UK)
  • very few, if any, have responded positively to it so far

The mosquito allergy test also does not change the final choice of treatment and is therefore not recommended by allergy doctors.

There is also an allergy test that can show if you are allergic to bee and/or wasp stings. Unfortunately, the test does not show anything about mosquito bites.


Allergy vaccination

Allergy vaccinations are not used against mosquito bites, but only against bee and wasp stings. The principle behind an allergy vaccination is that the patient is given a small amount of the insect venom to which they have developed an antibody. The venom is administered by injection and the course of treatment extends over a longer period of time (typically 3-5 years). During the course of treatment, the dosage is continually adjusted upwards, while the frequency of injections is gradually reduced (in practice, you start with many small frequent doses and end with a few larger doses). An allergy vaccination lasts for several years and in some cases even for life.


What diseases can mosquitoes transmit?

Mosquitoes can act as intermediate hosts for various diseases; i.e. they carry the disease without necessarily reacting to it themselves, but are able to infect new hosts when they suck blood from them. In practice, this means that a mosquito must bite an infected host in order to infect new hosts. 

Mosquitoes carry viruses and parasites in particular, which - if transmitted to animals or humans - can cause disease in the host. However, it is not certain that a virus or parasite will survive in the mosquito, nor is it certain that they can survive the host's immune system. Therefore, a bite from an infected mosquito does not necessarily mean that you will develop the disease in question.

The most common diseases transmitted by mosquitoes are:

  • Malaria
  • Dengue fever
  • Encephalitis (inflammation of the brain)
  • Yellow fever
  • West Nile virus
  • Meningitis (meningitis)
  • Zika virus

The symptoms of mosquito bites possibly being caused by something other than allergic reactions can be:

  • Fever
  • Severe headaches
  • Pain in the body
  • Nausea or vomiting
  • Rashes
  • Fatigue
  • Light sensitivity
  • Confusion
  • Neurological changes

Seek medical attention if you experience any of the above symptoms after a mosquito bite.