Insect venom allergy: description
Insect bites are never pleasant. While mosquito bites usually only itch violently, bee and wasp stings cause painful or itchy swelling and redness at the site of the bite. Such symptoms are due to ingredients in the insect saliva, which have a pro-inflammatory or irritant effect on the tissue, for example. They are normal and usually harmless.
The situation is different in the case of an insect venom allergy – i.e. an excessive reaction of the immune system to the venom that enters the body when some insects (such as bees, wasps) sting. Here, the immune system reacts violently against certain ingredients in the insect venom.
Common causes of insect venom allergy
In Central Europe, insect venom allergy is mainly caused by the stings of so-called Hymenoptera, including in particular the stings of certain wasps and honey bees. Less frequently, the allergy is due to other hymenoptera such as bumblebees, hornets or ants.
However, cross-reactions (cross-allergies) are often possible because the venom of some hymenoptera is similar in composition. Therefore, people with wasp venom allergy often also do not tolerate the venom of bees and hornets – due to structurally similar allergens. And a bee venom allergy can develop a cross-allergy to wasps as well as to bumblebees and certain components of honey.
Read more about this topic in the article Cross Allergy.
Can mosquito bites also trigger allergic reactions?
Generally not. Usually a local inflammation is responsible, triggered by proteins in the mosquito saliva. They dilate the blood vessels and inhibit blood clotting – so the mosquito can suck blood more easily. However, certain immune cells (mast cells) react to these foreign proteins by releasing the messenger substance histamine. It causes the local inflammation and itching – a general mechanism for defense against potentially dangerous intruders.
Histamine also plays an important role in allergic reactions. In the case of mosquito bites, however, its release is not usually allergic. Nevertheless, true allergy to mosquito bites is possible, but rare. If it occurs, in individual cases it can also cause general reactions such as nausea, palpitations or shortness of breath – like a severe insect venom allergy.
Insect venom allergy: symptoms
Not all reactions to an insect sting are allergic in nature:
Some people develop an increased local reaction (severe local reaction). It is probably allergic, although not necessarily mediated by IgE, but by other allergic mechanisms:
In this case, the swelling at the injection site expands to a diameter of more than ten centimeters and lasts longer than 24 hours. Sometimes lymphatic vessels also become inflamed (lymphangitis). Rarely, there is also a feeling of illness, headache and other accompanying symptoms.
Regardless of whether the local reaction is normal or increased: If the insect has bitten the mouth or throat, the local swelling of the mucous membrane can narrow or even close the airways!
General allergic reactions (allergic systemic reactions) in insect venom allergy can vary in severity. In milder cases, they are limited to the skin. Within minutes after the insect bite, symptoms such as:
- Itching
- Hives (urticaria)
- Skin/mucous membrane swelling (angioedema), for example on the face
In the case of a more pronounced insect venom allergy, allergic symptoms in the gastrointestinal tract, respiratory tract and cardiovascular system are added to the skin symptoms. Possible symptoms, depending on the severity, are for example:
- abdominal cramps, nausea, vomiting, intestinal or bladder leakage
- runny nose, hoarseness, respiratory problems up to an asthma attack @ heart palpitations, blood pressure drop
- heart palpitations, drop in blood pressure, shock
In extreme cases, an insect venom allergy leads to respiratory and cardiovascular arrest.
Read more about such a severe allergic (anaphylactic) reaction in the article Anaphylactic shock.
Insect venom allergy: causes and risk factors.
An insect venom allergy does not develop at the first sting. First, sensitization occurs: the immune system classifies certain substances in insect venom (e.g. hyaluronidases, phospholipases) as dangerous and develops specific immunoglobulin E (IgE) antibodies against them.
When stung again, the immune system, or rather the troop of specific IgE antibodies, “remembers” these foreign substances (called allergens). As a result, a cascade of defense mechanisms is triggered: Various immune cells (mast cells, granulocytes) secrete histamine, leukotrienes and prostaglandins. These pro-inflammatory messengers set in motion the allergic reaction, which can affect the entire body.
Risk factors for insect venom allergy
An increased risk of contact with insects (increased exposure risk) favors the occurrence of an insect venom allergy: Those who come into contact with bees or wasps more frequently are more likely to be stung more often. This applies, for example, to beekeepers or their family members and close neighbors. Fruit and bakery vendors are also often swarmed by insects such as wasps thanks to their wares.
Anyone who spends a lot of time outdoors also runs a slight risk of being stung by bees & co. and thus developing an insect venom allergy over time. This applies, for example, to gardeners, farmers, forestry workers and people who often go swimming, cycle a lot or regularly work in the garden.
There is an increased risk of severe reactions in the following cases, for example:
- older age (> 40 years)
- Asthma
- Cardiovascular diseases (such as high blood pressure, heart failure, heart attack, stroke, etc.)
- Mastocytosis – a rare disease in which very many or altered mast cells are found in the body. These further fuel the exuberant immune response.
- Wasp Venom Allergy
Insect venom allergy: examinations and diagnosis
If an insect venom allergy (such as bee or wasp venom allergy) is suspected, the doctor will first take the medical history during the initial consultation (anamnesis). He may ask the following questions, for example:
- Which insect stung you?
- What symptoms appeared after the sting? How quickly did they appear? How did they develop?
- Have you been stung by the same insect before? What symptoms did you experience then?
- Do you suffer from any chronic diseases? If yes, which ones?
- Are you known to suffer from any other allergies? If yes, which ones?
- Are you taking any medications? If yes, which ones?
Allergy tests (such as skin test, determination of specific antibodies) are usually only indicated if the symptoms are not limited to the injection site, but also affect other parts of the body (systemic reactions) – for example in the form of hives on the body, breathing difficulties or nausea.
Skin test
In the prick test, the doctor applies various allergens (such as those made from bee venom) in drop form to the inside of the forearm. He then lightly scores the skin at these points. It is then necessary to wait and see whether reactions occur at the affected skin sites. These indicate an allergic reaction. For example, in the case of a wasp or bee sting allergy, the skin may redden and begin to itch where the insect venom in question was applied.
Alternatively, or if the prick test is negative, the doctor can inject the allergens into the skin (intradermal test). In this case, too, he or she then checks for any hypersensitivity reactions.
The suspicion of an insect venom allergy is confirmed if specific immunoglobulin E antibodies against an insect venom (total) can be detected in the patient’s blood. In unclear cases, further examinations and tests may be considered. For example, one can search for specific IgE against important single allergens in insect venoms.
If specific antibodies to both wasp and bee venom can be detected, the patient is either sensitized to both insect venoms and allergic. Or he has only one of the two insect venom allergies (bee or wasp venom allergy) and reacts only in the course of a cross-reaction (cross-allergy) also to the other insect venom.
Insect venom allergy: treatment
Acute therapy of local reactions
- If the insect’s venom sting is still stuck in the skin (more likely in bee than wasp stings), it should be removed immediately – but carefully, so that more venom is not forced into the skin from the venom sac. Therefore, do not grasp with tweezers or fingers, but scrape the stinger away with a fingernail.
- Apply glucocorticoid cream or gel and possibly also apply a cooling moist poultice for about 20 minutes.
- Taking an antihistamine inhibits histamine action and thus relieves allergy symptoms. Afterwards, a visit to the doctor is recommended.
- In case of increased local reaction, the short-term use of a glucocorticoid preparation may be necessary.
Those who know about their insect venom allergy ideally have the necessary medication handy in an emergency kit and have discussed its correct use with a doctor in advance.
In case of an insect bite in the mouth or throat, do not give the person anything to drink – he could easily swallow due to the swelling of the mucous membrane.
Acute therapy of general allergic reactions
In the hopefully handy emergency kit are medications that the affected person can use in an emergency before the arrival of the doctor (immediately alert the rescue!):
- a fast-acting antihistamine to be taken in order to stop the allergic reaction mediated by histamine
- A glucocorticoid to take by mouth or as a suppository (for young children): Has an anti-inflammatory effect and suppresses immune reactions.
- Adrenaline in an auto-injector: It stabilizes the circulation and is simply injected into a muscle by the patient or an assistant.
Affected persons with severe allergic symptoms must be hospitalized and usually remain there for some time for monitoring, since physical reactions may still occur later.
Hyposensitization
Some insect venom allergies can be treated causally by so-called hyposensitization (specific immunotherapy). In the course of several sessions, the allergy sufferer receives increasing amounts of “his” allergy trigger injected under the skin. In this way, the immune system is supposed to slowly “get used” to the allergen, so that the insect venom allergy weakens significantly over time.
Hyposensitization is indicated for severe insect venom allergy. Its effectiveness is well documented. However, it is usually a lengthy process that can take years. In addition, it is not suitable or possible for everyone affected.
You can read more about the duration, procedure and risks of specific immunotherapy in the article Hyposensitization.
In most cases, hypersensitivity reactions to insect venom do not leave any permanent damage. However, deaths due to severe allergic reactions to insect stings do occur time and again. The number of unreported cases is probably higher, since anaphylaxis often goes unrecognized as the cause of death.
Hyposensitization often offers protection against systemic reactions in the case of insect venom allergy: studies have shown that it is more than 95 percent effective in the case of wasp venom allergy and between 80 and 85 percent effective in the case of bee venom allergy.
Insect venom allergy: prevention of insect bites
Allergy sufferers should avoid bees, wasps, hornets, bumblebees and mosquitoes whenever possible. Various measures can help keep insects away, especially during the warm season. The most important are:
- Avoid eating sweet foods and drinks outdoors if possible.
- Stay away from trash cans, garbage baskets, animal enclosures, and fallen fruit – as well as bee hives and wasps’ nests.
- Don’t walk around barefoot outdoors, especially across meadows. Closed-toe shoes are better.
- Wear long-sleeved clothing when outdoors. Tighter-fitting and light-colored clothing is favorable. Loose-fitting and dark clothing is unfavorable. Avoid colorful clothing (bees especially love the color yellow).
- Avoid perfumes and other cosmetics with fragrances (can attract insects).
- Do not make frantic movements near stinging insects (especially wasps). Do not shoo them away even if they have already settled on their apple strudel or drinking glass.
- Keep apartment windows closed during the day or install an insect screen.
- Do not turn on the light in the evening or at night when the window is open (hornets are nocturnal).
