Which insects sting and how?

Insects that sting are members of the hymenoptera class of insects:

• Vespids: yellow jacket, hornet and wasp
• Apids: bumblebee and honeybee.

The stinging apparatus is located in the abdomen of the female insect and consists of a sac containing venom and a barbed stinger.

When a bee stings, the apparatus becomes detached from the insect leading to its death, hence bees can only sting once. Wasps can sting multiple times and do not leave their sting behind in the skin.

Symptoms of a bee or wasp sting

A sting from a wasp causes a sharp pain that usually lasts for a few seconds. The area that has been stung often become red, painful and swollen. It may cause local irritation, itching or pain for hours to days afterwards.

A sting from a bee feels similar to that from a wasp however it leaves a sack filled with venom in the skin.

The range of reactions to stings

Most people suffer only minor symptoms after a sting. However some people suffer more severe or even life-threatening reactions.

Minor localised reaction

• The site of the sting becomes red and slightly painful or itchy for a few days.
• Blistering may develop.

Blisters following a bee sting

Bee sting reaction

Wasp sting reaction

Large localised reaction

• The affected area may swell and become painful.
• The swelling may last between 48 hours and seven days, and can often be confused with cellulitis.[1]
• Similar reactions occur with subsequent stings, with the risk of anaphylaxis being less than 5% per episode.[2]

Reaction to a bee sting

Reaction to honey bee sting

Reaction to a honey bee sting

Systemic reaction

Life-threatening allergic reactions due to anaphylaxis are rare. They are more likely in people that have been stung before, because of sensitisation to the insect venom.

• Symptoms usually start within 10-20 minutes of being stung, but may occur up to 72 hours later.
• The clinical features are the same as anaphylaxis due to other causes, and include urticaria, flushing, angioedema, life threatening circulatory collapse, and bronchospasm. It may be fatal.
• The incidence of anaphylaxis to bee stings in the general population is estimated to be 0.3-3%.[1]
• Toxic reactions leading to anaphylaxis can occur in people who have suffered multiple simultaneous stings (between 50-100), as the large amount of venom stimulates IgE production.

Localised reaction to multiple wasp stings

What should you do if a bee or wasp stings you?

A bee's sting should be removed immediately from the skin. As a wasp does not leave its sting behind you cannot remove it. Avoid squeezing more venom from the sack of a bee sting into the skin when trying to remove it with fingers or tweezers. It is best scraped off with a flat card.

The severity of the reaction will determine if any medical treatment is needed.

• Wash the local area with water and keep it clean.
• Try not to scratch or rub the area.
• Use a cold compress over the area to help to reduce swelling.
• Simple analgesia is usually adequate, for example paracetamol (American name acetaminophen) or ibuprofen.
• Oral antihistamine tablets reduce itch and swelling
• Topical ‘bite or sting’ creams can give some symptomatic relief. They usually contain local anaesthetic, antihistamine, or corticosteroid.

A large localised reaction with severe swelling may warrant a course of oral steroids, for example prednisone for 3-5 days.

Life threatening reaction or anaphylaxis is a medical emergency.

• Adrenaline (eg, EpiPen®) should be administered if available for anyone with signs of shock, breathing difficulty, or airway swelling.
• In hospital, Advanced Life Support (ALS) protocols should be followed.
• Those who are at risk of anaphylaxis should be supplied with an EpiPen and counselled, along with their close relatives, responsible adults, or carers, about how and when to use it.

Unusual reactions to bee and wasp stings

Bee and wasp sting reactions are sometimes very persistent, lasting weeks or months.There have been case reports of vasculitis, serum sickness, neuritis and encephalitis occurring in the days to weeks following insect stings [3]. There are even reports of secondary parkinsonianism and cerebral infarction following hymenoptera stings [4,5]. Some of these have occurred after anaphylactic reactions to stings.

Persistent wasp sting reaction

Purpuric wasp sting reaction

Infected bee and wasp stings

Cellulitis and lymphangitis can occur if bacteria enter the break in the skin at the site of the sting. Infection should be treated with antibiotics.

Skin and serum allergy testing

Skin prick tests and serological reactivity testing can be performed to identify those who may suffer more severe reactions from insect stings. This is useful to identify where venom immunotherapy (VIT) would be of benefit.

Immunotherapy for insect stings

Venom immunotherapy (VIT) is an effective treatment to protect venom allergic people from sting-induced anaphylaxis [6]. It is not generally indicated for adults with reactions limited to the skin (eg, urticaria, angioedema, or erythema).

Venom immunotherapy is usually performed by an immunologist or allergy specialist. It involves a course of injections containing a very small amount of the allergen, which in this case is insect venom. The injections are given under the skin repeatedly over a prolonged period of time, often several years. The amount of venom injected is slowly increased throughout the course. Eventually desensitisation occurs, meaning the body becomes less sensitive to the venom.

Bee venom reaction from immunotherapy

Preventing insect stings

Simple measures can be taken to reduce the risk of being stung by these insects.

• Watch out for wasps, bees, hornets and their nests if around flowering plants, fruit trees, and rubbish.
• Keep your skin covered with long sleeves, trousers and shoes.
• If a stinging insect is flying around you, try to move away slowly without waving your arms around.
• Apply insect repellent to exposed skin; DEET is thought to be the most effective.
• Avoid areas that attract wasps, bees, and hornets, including flowering plants, rubbish, fruit trees, wasp or bee nests.
• Keep food and drink covered when outside.
• Avoid wearing bright clothes, particularly yellow, when stinging insects are likely to be around.
• Try not to bother wasps and bees. If a wasp nest is near your house, have a pest control expert visit to get rid of it.