We all get stung or bitten by insects every now and then – and most people end up with a small, red, itchy bump as a result. But those who are allergic to insect stings or bites may react strongly, and the reaction might even be life-threatening in rare cases.
In insect venom allergies, the body’s immune system attacks certain parts of proteins that enter the body when the insect bites or stings. Some people are generally more likely to have allergies. But it isn’t known why some people have an insect venom allergy and others don’t. This allergy doesn’t develop after the first sting or bite, either: Sometimes people get stung or bitten over many years without having an unusual reaction. Over time, though, their bodies become more sensitive to the venom in the sting or bite (sensitization) and they then suddenly have an allergic reaction to it.
Allergic reactions to insect venom cause the skin around the bite or sting to become very swollen. The swelling often has a diameter of more than 10 cm and lasts longer than 24 hours. It usually hurts, burns or itches a lot.
Stings inside the mouth or throat can cause the airways to become swollen and narrow, making it harder to breathe. This is more likely to happen in people who are allergic to the insect venom. But the swelling is rarely bad enough to lead to suffocation.
The allergic reaction can also affect the whole body, though. This is known as anaphylactic shock. Sometimes it’s mild, but it can also be life-threatening. The milder reactions include hives (a raised skin rash – also known as nettle rash), itching all over the body, dizziness, stomach and bowel problems, and nausea. People may also generally feel weak, have a swollen face or hands, or have problems swallowing. Severe anaphylactic shock leads to breathing problems, a drop in blood pressure, loss of consciousness or even cardiac arrest.
The allergic reactions usually occur soon after the person is bitten or stung. In rare cases, though, they may only occur a few hours later. Sometimes the symptoms of anaphylactic shock get better at first and then come back again within eight hours.
Causes and risk factors
Bee sting allergies and wasp sting allergies are the most common allergic reactions to insect venom. Bee stings are more likely to lead to serious allergic reactions than wasp stings are. Allergic reactions to hornet stings (usually in people who are allergic to wasp stings) or bumble bee stings (usually in people who are allergic to bee stings) are much less common. Mosquito bites, horsefly bites and ant bites hardly ever lead to allergic reactions in Germany and similar countries, apart from near to the area of skin that was bitten.
Knowing the difference between the behavior of bees and wasps can help to avoid them and react properly if you get stung. And knowing which insect stung you can be important for the diagnosis:
About 2% of the population react to insect bites and stings with symptoms that affect more than just the surrounding area of skin.
Some people are stung or bitten more often than others, and are more likely to become allergic to the venom as a result. These include beekeepers and people who live with them. Other people who are at higher risk include those who work in bakeries, sell fruit or work on a farm.
Generally speaking, allergic reactions to insect bites or stings don’t have any lasting harmful effects.
About 20 deaths due to bee sting, wasp sting, or hornet sting allergies are reported every year in Germany. The actual number is probably a little higher because allergic reactions aren’t always recognized as the cause of death.
Before performing a physical examination, the doctor will first ask about the exact symptoms. It isn’t always easy to tell the difference between wasp stings and bee stings, so it’s important to describe where you were when you were stung, and how the insect was behaving at the time. Although people usually say they have a wasp sting or a bee sting, these insects often get mixed up.
In the skin test, a solution containing insect venom is put on an area of superficially scraped skin to see whether the skin becomes red, swollen or itchy. In the blood test, the doctor checks whether a blood sample contains antibodies to insect venom.
Unlike with other kinds of allergies, provocation tests generally aren’t done if it is thought that someone may have an insect venom allergy. In provocation tests, the body is exposed to increasing doses of the suspected trigger in order to see whether there’s an allergic reaction. But this test can lead to severe reactions in people with insect venom allergies, so it is only done in exceptional cases and in specialized centers.
The main way to prevent allergic reactions is to avoid being bitten or stung by the insect. To lower the risk, the following strategies are recommended:
- Be careful when eating outdoors, and clear the table as soon as you have finished eating. Avoid eating outdoors if there are a lot of insects flying about.
- Don’t spend time near rubbish.
- Cover up your drinks and use a straw.
- Clean your mouth and hands after eating.
- Don’t swat at wasps or bees – most insects defend themselves by stinging. Stay calm and move slowly.
- Cover up your skin with clothing.
- Keep windows closed during the day.
- Stay away from beehives and wasps’ nests.
The best way to deal with insect bites and stings will mainly depend on the symptoms that occur and whether the person has been “desensitized.” To start off with, antihistamines are taken in the form of a tablet. Depending on how severe the skin reaction is, a steroid medication may be used too. If more serious symptoms develop – such as breathing problems, nausea, circulation problems or swelling in the mouth and throat – adrenaline must be injected as soon as possible.
People who tend to have more severe allergic reactions are often advised to have allergen-specific immunotherapy (also known as desensitization). After having this treatment, the allergic reaction to the insect sting is usually much weaker, or they may even no longer be at all allergic to it.
People who have a confirmed insect venom allergy are advised to carry a medical ID card or bracelet on them at all times, to let people know what they are allergic to in an emergency.
Boyle RJ, Elremeli M, Hockenhull J, Cherry MG, Bulsara MK, Daniels M et al. Venom immunotherapy for preventing allergic reactions to insect stings. Cochrane Database Syst Rev 2012; (10): CD008838.
Casale TB, Burks AW. Clinical practice. Hymenoptera-sting hypersensitivity. N Engl J Med 2014; 370(15): 1432-1439.
Pryzbilla B, Rueff F, Walker A, Räwer H-C, Aberer W, Bauer CP et al. Bienen- und Wespengiftallergie, Diagnose und Therapie: AWMF-Register-Nr.: 061 - 020. Allergo J 2011; 20: 318-339.
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