Mosquito bites are not generally considered dangerous, but some people can experience a severe allergic reaction to them. As well as life-threatening reactions that cause the windpipe to swell up and interfere with breathing, an allergic reaction to a mosquito bite may be as mild as a simple itchy, red area around the bite. The intensity of a reaction to a mosquito bite is related to the amount of times the person has been bitten.

When a mosquito bites a person, it breaks through the skin. The body recognizes the saliva from the mosquito in the bite as foreign. Generally, the body produces small bumps with accompanying itching where the insect bit. The immune system learns from experience, so the next time a mosquito bites the person, the immune response is quicker, and can be much more intense.

Instead of a small area responding to the bite, a strong allergic reaction to a mosquito bite can occur. Where the last bite only produced a mildly irritating itch and lump, the new bite results in a large area of inflammation, where the skin is red and swollen. Itchiness is also typically present.

This form of allergic reaction to a mosquito bite is mild enough, although unpleasant. It can take up to two days to manifest itself after the bite. Although the reactions to the bite do tend to worsen after the initial recognition of the mosquito saliva by the immune system, in countries where mosquitos are very common, the opposite can also occur. Adults who have had many bites throughout their life tend to become less sensitive to the saliva, and therefore do not experience as many symptoms as those who rarely experience bites.

A much more serious form of allergic reaction to a mosquito bite is anaphylaxis. This is a potentially deadly condition where the immune system produces an over-the-top reaction to the saliva, and endangers the life of the person. Skin rash, blotchiness or hives are some of the signs of this reaction. The anaphylaxis can also close the airways, and cause wheezing and difficulty breathing. The throat can swell up, along with the face, and the person may have skin itchiness throughout his or her body.

Other symptoms of anaphylaxis include diarrhea and vomiting. Unusual anxiety and fainting spells can also occur. Anaphylaxis can also speed up the heartbeat. All of the symptoms require medical treatment straightaway. Other issues such as fever, headache or an increase in the size of lymph glands may point to a mosquito-borne disease, especially if the person has been in an exotic country recently.

People at risk of allergic reaction to a mosquito bite can reduce the risk by using insect repellent and staying inside at dusk and dawn, when the insects feed. Clothing that covers exposed skin can also help. According to the Mayo Clinic, washing the area of a new bite with soap and water may reduce the localized allergic reaction.