Allergies to Insect Stings information from Treatallergies.com

Allergies to Insect Stings

Many people have allergies to stinging insects (hymenoptera) but only a small number of these are at risk from a life-threatening anaphylactic reaction. About two million Americans are believed to be allergic to insect stings. Surveys estimate that only a small percentage of the general population, between 1% to 5%, are susceptible to such dangerous systemic allergic reactions. Most people who exhibit positive reactions to insect venoms in skin tests will experience only localized reactions to stings. A Skin Prick Test and RAST (Radioallergosorbent Test) blood testing can merely confirm the presence of IgE antibodies, not the severity of the reaction, and up to 20% of patients who have positive skin test have negative RAST tests for venom allergies. The Skin Prick Test involves a small drop of allergen solution being put on the skin of the forearm and being pricked using a fine point. If the person has antibodies to the allergen then a small, itchy bump will appear within ten minutes. This area of skin will quickly settle down once again and return to normal.

Allergies to insect stings usually develop before the age of 20. Many people with sting allergies do exhibit a reduced susceptibility over time but, in about half of all cases, the allergy will persist for the rest of their life. Up to 50% of children with systemic reactions will lose this sensitivity within a decade. An average person can safely tolerate 10 stings per pound of body weight, which translates roughly into them being able to withstand more than 1000 stings. If they are allergic to stings, then it could only take one sting to precipitate a fatal anaphylactic reaction.

The allergic reaction that occurs after someone is stung is caused by the venom associated with the sting. Insect venom contains a complex mixture of proteins and peptides, while the smaller peptides such as histamine and serotonin cause painful skin reactions. Local reactions to the sting are typically confined to the area surrounding the sting. Systemic reactions will involve many other area of the body and includes swelling (angioedema), "hives" (urticaria), or, most seriously, anaphylaxis. Those who are allergic to the venom will also react to the larger proteins present, including phospholipase. The body mistakes these proteins, or allergens, for much more threatening intruders, prompting an overreaction in response. The immune system produces IgE antibodies which bind to mast cell receptors. The next time the body is exposed to the same allergen, the IgE antibodies trigger chemicals, including histamine, to fight the invader that it recognises from its previous encounter.

There are two major subgroups of stinging insects. Honeybees and bumblebees are apids that will only sting you if provoked. Honeybees will only sting once before they die. Wasps, hornets, and yellow jackets are examples of vespids that are more prone to sting at anytime and can sting repeatedly. Generally those people who are allergic to wasp venoms will also be susceptible to the venom of other species of wasp because of the high degree of cross-reactivity amongst different types of vespids. They will, however, probably not have the same reaction to bee venom. Also, if you are allergic to bee venom, then you are also likely to react to bumblebee venom.

In New Zealand, common insects with stings include bumblebees (Bombus sp.), Italian honeybees (Apis mellifera), common wasps (Vespula vulgaris), German wasps (Vespula germanica), Tasmanian wasps (Polistes humulus) and Asian paper wasps (Polistes chinensis). In America, bees, wasps, hornets, yellow jackets, and fire ants can all cause problems to those with a sting allergy.

Sometimes people, especially children, can develop large local reactions to mosquito or sandfly bites. This is generally because they have an allergy to the proteins present in the saliva of insects. This sort of allergy will usually abate over time, becoming less severe with each subsequent season. These reactions can be treated as usual with antihistamines creams or tablets.

If you get stung, you should apply ice to the site of the sting to reduce swelling. If stung on the hand, remove any rings from your fingers immediately, before swelling occurs. A tourniquet can be applied to the affected limb to slow venom absorption. If the stinger has been left in the skin, as occurs with a bee sting, it should be removed in such a way that you avoid squeezing the attached venom sac or else this will result in more venom being injected into the system. The stinger should be flicked or scraped off with a fingernail, knife, credit card, a piece of paper, or a similar flat object. Other stinging insects, like the vespids, will not leave a stinger behind. If a pronounced local reaction occurs, it may be able to be treated with an antihistamine.

Do not scratch the site of the sting. This will only force the irritating substances deeper under the skin. Wash the sting site with soap and water, and apply an antiseptic. Apply a hydrocortisone cream directly to the area and cover with a dry, sterile bandage. Take an oral antihistamine to reduce "hives", itching, and swelling.

Most people are not allergic to insect stings and may mistake a normal or localized reaction for an allergic one. The symptoms of a mild, localized allergic reaction are similar to what most people experience but is more pronounced. It can result in the following symptoms near the sting site:

Pain
Reddening of the skin
Mild to moderate swelling
Raised, pimple-like spots
Feeling of warmth
Itching

These symptoms will usually only cause discomfort in the initial 24 to 48 hours, after which time they will disappear, but they can persist for longer. They should remain relatively localized around the sting site. If a person is stung on the ankle, however, the swelling may affect the entire leg but this is still considered a localized reaction.

Symptoms of a severe systemic allergic reaction may include:

Difficulty breathing, wheezing
"Hives", a red, itchy rash that spreads beyond the sting site
Swelling of the face, eyes, mouth, tongue or throat, resulting in difficulty swallowing
Anxiety, rapid pulse rate, restlessness
Tightness in the chest
Dizziness
A sharp drop in blood pressure
Unconsciousness
Nausea, vomiting
Anaphylactic shock can occur in around 10 minutes in cases of an extreme allergic reaction

It has been estimated that anaphylaxis is responsible for around 40 to 50 deaths in America every year. If an anaphylactic reaction occurs, adrenaline in the form of an EpiPen intramuscular injection should be quickly administered.

Tips if you are allergic to insect stings

Certain precautionary steps can be taken to reduce the chance of being stung:

Wear enclosed footwear and socks when walking outdoors.
Cover exposed limbs when outside with long-sleeves, long pants, etc.
Avoid wearing strong perfume, cologne, strongly scented lotions, hair sprays, or deodorants that may attract insects.
Avoid eating sweet foods or fruit outdoors. Cover food at picnics, etc.
Avoid wearing bright, colourful clothing.
Depose of rubbish carefully and stay away from open rubbish bins that contain rubbish or rotting fruit that may attract insects like wasps.
Take care in the garden or anywhere else that may conceal a nest or hive. If you discover one of these on your property, call a professional pest control agent to have it eradicated.
Use insect screens on the windows and doors of your home.
Drive with car windows closed.
Remember that wearing insect repellent will only discourage smaller insects and will not repel wasps and bees.
Remove any insect attracting plants or vines growing in or around your house.
Be careful when drinking from open drink cans. Stinging insects may be attracted to crawl inside the can, unbeknownst to you.

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