Why do Mosquito Bites Itch?

When a person is bitten by a mosquito, red marks or bumps may develop and they tend to be itchy, thereby causing discomfort. Some people may experience severe swelling as well. Mosquito bites are usually harmless, however, in some cases there may be a risk of getting affected by malaria, dengue fever, and other infections.

The itching that one feels when he/she gets bitten by a mosquito and the bump that develops are actually a response of the immune system to antigens that are present in the mosquitoes saliva.

When a mosquito bites a person, it injects a bit of its saliva, which acts as a 'local anesthesia', so one would be unaware for a few seconds that he/she has been bitten. It also acts as an anticoagulant, preventing the blood from clotting so the mosquito can be free to draw blood for as long as it pleases.

The body sends the IgG and IgE antibodies to deal with this sudden invasion of foreign proteins (antigens) that have entered with the mosquitoes saliva, thus, leading to a normal immune response of swelling and itching.

The cause of itching and swelling could be an allergic reaction (which could be severe) which is a little more than others' reaction to the bite. Another reason may be that one would not have been bitten before. In kids, this is often the case and adults gradually develop an immunity or resistance against the antigens making their body react less seriously.

They itch longer because the antibodies are busy at work at the site of entry of the antigens through which the mosquitoes have entered. Thus, the more one scratches, the more the bite itches and the longer it does as well.

They itch more at night because of the decreasing levels of the steroid hormone, cortisol, which can reduce the immune response. At night, the cortisol levels are quite low, thus increasing the immune response, and causing more itching and swelling at night.

This can vary in people and also by the light/dark cycle that our body responds to, because cortisol production depends on our circadian rhythm or the day/night cycle.

A mosquito chooses its victims by the smell they give out, and prefers people with a greater proportion of carbon dioxide in their sweat and the presence of a chemical known as Nonanal. Thus, there are three types of people that are very popular with mosquitoes: men, obese individuals, and people with the 'O' blood type.

At times, the antigens are not completely removed and it may take a couple of days for the symptoms to reduce. If after almost a week the symptoms have not reduced or have worsened, it is better to consult a doctor. Some people get adverse reactions to infected mosquito bites, with the skin developing blisters or scabs.

To ease the itching and swelling, one could try applying calamine lotion or vinegar on the affected area. Excessive scratching should be avoided as this could lead to bruising the skin and infection.

Disclaimer: This is for informative purposes only, and should not be used as a replacement for expert medical advice.