Insect Bites and Stings: Treatment and Management | Doctor

Insect Bites and Stings

In this article

• How common are insect bites?
• How to identify an insect bite
• What is the treatment for insect bites and stings?
• Hymenoptera stings
• Blood-sucking flies
• True bugs (Hemiptera)
• Ticks (Ixodoidea)
• Harvest mites (Trombiculidae)
• What are the complications of insect bites and stings?

How common are insect bites?

^[1]

Insect bites tend to be seasonal and increase during the summer months when more insects are active and more skin is exposed. Studies suggest that 56-94% of people are stung by insects such as bees, wasps or ants, at least once in their lifetime. In the UK, insect stings are the second most common cause of anaphylaxis outside of medical settings.

Insect venom induces a toxic reaction at the site of the sting. Large local reactions are due to allergy. In the UK, wasp venom allergy is more common than bee venom allergy, and biting insects rarely cause systemic reactions.

A German study found that large local reactions occurred in up to 25% of the population, and as many as 3.5% develop IgE-mediated, potentially life-threatening anaphylaxis, of which about 20 people die in Germany each year.^[2]

How to identify an insect bite

The cause of a bite can often be readily diagnosed where an insect remains attached, as in ticks (small blood-sucking bugs often thought of as insects) and with bloodsuckers that are highly visible – eg, mosquitoes, midges and black flies. Others may not be so easy to diagnose because they bite at night or when the patient is asleep – eg, some mosquitoes, sandflies, bedbugs and triatomine bugs, or when it is inconspicuous and does not cause an immediately painful bite – eg, harvest mites, some fleas and biting flies. Bites typically result in single or grouped pruritic erythematous papules. Some may have a central punctum and others may be bullous.

There is often a skin reaction to an insect bite and this may lead to pruritus and urticarial papules and sometimes to secondary bacterial infection. As well as a local reaction, the bite may cause an anaphylactic reaction and may act as a vector of disease.

Human, dog, and cat fleas, as well as bedbugs, feed by biting their victims, causing acute prurigo, which is aggravated in sensitised victims (papular urticaria). Diagnosis is based on three or more bites (in most cases three) with pruritic, erythematous-oedematous papules, which are either linear or triangular, a few centimetres apart. This pattern is known as the ‘breakfast, lunch, and dinner’ sign.^[3]

General management measures include cooling the skin, use of calamine and antihistamines to reduce itching, antibiotics for secondary bacterial infection if one develops and any specific treatment for disease transmitted as a result of the bite.

What is the treatment for insect bites and stings?

^{[1, 4]}

• If a stinger is visible in the skin, remove it as quickly as possible by scraping sideways with a fingernail or a piece of card.
• Clean the area and advise that simple first aid measures such as the use of cold compresses may help reduce local pain and swelling.
• Advise the person on prevention of secondary infections with good hygiene and avoidance of itching.
• Simple pain relief with paracetamol or ibuprofen.
• Oral antihistamines or topical corticosteroids (such as hydrocortisone 1%) may help reduce itching associated with cutaneous reactions but good-quality evidence in support of this use is lacking.
• If secondary infection develops, treat cellulitis with oral antibiotics in accordance with local prescribing protocols.
• Arrange immediate admission to hospital in the following circumstances:
• Systemic hypersensitivity or toxic reaction to an insect sting or bite.
• Previous systemic allergic reaction to the same type of bite or sting.
• Severely immunocompromised and symptoms or signs of an infection.
• Stung on the mouth, throat or tongue and is at risk of airway obstruction.
• Stung around the eyes and is at risk of compromised vision.
• Cellulitis that is associated with systemic effects or is worsening despite treatment in primary care.
• Fever or persisting lesions associated with a bite or sting which occurred whilst travelling outside the UK.
• Bitten or stung by an unusual insect or one from a tropical or sub-tropical area.

Antibiotics for insect bites and stings

^[5]

• Most insect bites or stings will not need antibiotics.
• First-choice antibiotic is flucloxacillin. Alternative first-choice antibiotics for penicillin allergy or if flucloxacillin is unsuitable are clarithromycin, erythromycin, doxycycline.
• First-choice antibiotic if infection is near the eyes or nose (consider seeking specialist advice) is co‑amoxiclav.
• Alternative first-choice antibiotics if infection is near the eyes or nose for penicillin allergy or if co‑amoxiclav is unsuitable are clarithromycin with metronidazole.
• Alternative-choice antibiotics for severe infection are co‑amoxiclav, cefuroxime, clindamycin or ceftriaxone.
• Antibiotics to be added if meticillin-resistant Staphylococcus aureus infection is suspected or confirmed (combination therapy with an antibiotic listed above; other antibiotics may be appropriate based on microbiological results and specialist advice) are vancomycin, teicoplanin or linezolid (if vancomycin or teicoplanin cannot be used; specialist use only).

Hymenoptera stings

• Insects of the order Hymenoptera include bees, wasps and ants.
• Stings from these insects can cause fatal anaphylaxis.
• The insects of Hymenoptera most relevant in the UK are wasp (Vespula vulgaris) and honey bee (Apis mellifera). Hornets (Vespa crabro) are also found in Britain, more commonly in the South of England.
• Wasp venom allergy is more common in the UK. Bee venom allergy usually occurs in beekeepers, their household members or where there is occupational risk.
• The risk for systemic reactions is increased by 58% if preceded by a sting within two months, even if the first sting was well tolerated.
• Venom allergy is not more common in atopic individuals.
• Some local reactions can be large and troublesome and are characterised by oedema, erythema or pruritus.
• An area of induration with a diameter of 10 cm and which peaks between 24 and 48 hours and then subsides is referred to as a large local reaction (LLR).^[6]
• LLRs occur in up to 26% of people and systemic reactions can occur in up to 7.5% of people who are stung.
• The likelihood of anaphylaxis from a future sting following an LLR is around 5%.^[7]
• However, when there is a history of anaphylaxis from a previous Hymenoptera sting and the patient has positive skin tests to venom, at least 60% of adults and 20-32% of children will develop anaphylaxis from a future sting.

Systemic reaction to wasp or bee stings

• Venom allergy is a common cause of anaphylaxis and may be fatal.
• Food, medications and insect stings are the three most common triggers of anaphylaxis.^[8]

However, anaphylaxis due to insect stings is still under-appreciated and undertreated.^[9]

The main features of systemic reactions are:

• Rapid-onset generalised urticaria.
• Angio-oedema.
• Bronchospasm and/or laryngeal oedema.
• Hypotension with collapse and loss of consciousness.

Investigation of patients with bee or wasp sting allergy

^[10]

• All patients who experience a systemic reaction to wasp or bee stings should be referred to an allergy specialist for investigation and management.
• Minor local reactions to insect stings are normal and do not warrant allergy testing.
• Skin testing (skin prick and intradermal) is the first line of investigation.
• This is with standardised venom extracts with both bee and wasp venoms and positive (histamine) and negative controls.
• Skin testing provides greater discrimination between bee and wasp sensitisation than serum-specific IgE to whole venom.
• Skin tests are also more often positive than serum-specific IgE and correlate better with history.
• Baseline tryptase should be measured. Those with raised levels have a higher risk of severe systemic reactions.

Treatment of patients with bee or wasp sting allergy

• All patients with a history of systemic reaction should be immediately provided with a written emergency management plan, an adrenaline (epinephrine) auto-injector and education in its use.
• With children, appropriate liaison with the school is recommended.
• Venom immunotherapy (VIT) is recommended for all patients with a severe systemic reaction after a sting. It reduces the chances of a serious allergic reaction to an insect sting and improves quality of life. ^[11]
• VIT is the only specific treatment that is currently available for patients with a history of systemic reaction to a Hymenoptera insect sting.
• VIT is effective in 95% of patients allergic to wasp venom and about 80% of those allergic to bee venom.
• VIT is not often recommended for children.
• A Cochrane review found that approximately 1 in 10 people treated had an allergic reaction during their treatment.^[11]
• The usual duration of VIT is three years in the UK.
• All patients should be advised of measures to reduce their risk of future stings. These include:
• Wear light-coloured clothing.
• Avoid strong fragrances, perfumes and highly scented shampoos.
• Wear shoes while outdoors and cover the body with clothing and a hat; use gloves while gardening.
• Avoid picking fruit from the ground or trees.
• Avoid drinking out of opened drink bottles or cans to prevent being stung inside the mouth.
• Wash hands after eating or handling sticky or sweet foods outdoors (especially children).
• Keep uneaten foods covered, especially when eating outdoors.
• Always contact professionals to remove bee or wasp nests.
• Wear full protective clothing while handling bees.

Management of bee or wasp stings

• The majority of people will have a localised reaction to a sting.
• Patients should be given antihistamines. Those with large local reactions may need oral prednisolone.
• Those with infected bites or stings will need oral antibiotics, usually in addition to oral antihistamines.

Blood-sucking flies

• Worldwide, these are held responsible for the spread of a large number of diseases, including malaria, filariasis, yellow fever, dengue, onchocerciasis, trypanosomiasis, leishmaniasis and loiasis.
• In the UK, these are usually only a nuisance. Discomfort of a bite is followed in sensitive individuals by pruritus with scratching and possible secondary infection.
• Where possible, the problem can be minimised by wearing clothing that covers the skin, and with use of insect repellents.

True bugs (Hemiptera)

• In the UK, the only medically significant species is bedbugs (Cimex lectularius).
• There is no evidence that they transmit disease. They may cause sleeplessness and bites may be painful and swollen. Bedbugs hide during the day and feed at night. They are found by searching the bedding at night or their hiding places during the day.
• They superficially resemble lentils and can live for six months without feeding, becoming paper thin. Control is by removal or steam cleaning of infected mattresses and treatment of the room with insecticide.
• In South America, triatomine (reduviid) bugs transmit trypanosomiasis.

Ticks (Ixodoidea)

• Worldwide, tick bites are responsible for the transmission of both rickettsial and viral infections and Lyme disease.^[12]
• In America, Rocky Mountain spotted fever, Colorado tick fever and Lyme borreliosis.
• In Australia, Q fever, tick paralysis, Queensland tick typhus and worldwide tick typhus.
• Soft ticks are widely distributed and can cause endemic relapsing fever.
• Ticks attach to the skin and feed with a barbed hypostome and then detach when engorged.
• The bites are usually painless but can cause local sensitisation and secondary infection.
• In the UK, most common ticks on humans are sheep tick (Ixodes ricinus), a vector of Lyme disease, and hedgehog tick (Ixodes hexagonus).
• Where there is tick infestation, bites can be avoided by tucking trousers into boots and the body should be searched after leaving the area to allow prompt removal of ticks, which can reduce risk of disease transmission.

Treatment and management of tick bites

• There are many suggested ways for removing ticks, including, but not limited to, heat, alcohol, and Vaseline®. None of these methods is recommended and they may, in fact, agitate the tick – in the case of the paralysis tick, this can cause more toxin to be expressed into the victim.
• A method that works well and minimises further expression of tick fluids is to lay small forceps along the skin with the ends either side of the tick’s head, press down into the skin and firmly grip the head of the tick. Then steady traction can be applied perpendicular to the skin, without twisting, until the tick is finally released. The aim is not to break the tick so that mouth parts are left in the wound. If remnants do get left behind use local anaesthetic and scrape them away carefully with a scalpel blade.
• In an area of significant Lyme disease incidence, doxycycline for ten days is the antibacterial of choice for early Lyme disease. Amoxicillin, cefuroxime or azithromycin are alternatives if doxycycline is contra-indicated.
• If there is significant paralysis then tick antivenom can be administered in addition to supportive care.

Harvest mites (Trombiculidae)

In Britain during late summer, larvae of the harvest mite (Neotrombicula autumnalis), which are tiny and often not noticed, may attach under tight-fitting clothes, feed and then detach causing itchy lesions that are sometimes bullous.

What are the complications of insect bites and stings?

^[1]

• Local skin trauma.
• Allergic reactions:
• Small local reactions, causing erythema, swelling, itching and pain.
• Large local reactions, with larger areas of oedema, erythema, and pruritus.
• Systemic reactions, which range from mild to life-threatening and include urticaria and angio-oedema, bronchospasm and upper airway obstruction, arrhythmias, coronary artery spasm, hypotension and shock, nausea, vomiting, diarrhoea, and abdominal pain, and seizures.
• Systemic toxicity: multiple bee or wasp stings can precipitate hypotension, diarrhoea, vomiting, headache, and shock.
• In rare cases, serum sickness, vasculitis, neuritis, encephalitis, and nephrosis have been reported after insect stings.
• Transmission of infectious disease such as Lyme disease.
• Secondary bacterial infection such as cellulitis and impetigo.
• Exacerbation of atopic eczema.
• Psychological distress from infestations such as bedbugs and scabies.

• Insect Bite Reaction; DermIS (Dermatology Information System)

• Juckett G; Arthropod bites. Am Fam Physician. 2013 Dec 1588(12):841-7.

• Singh S, Mann BK; Insect bite reactions. Indian J Dermatol Venereol Leprol. 2013 Mar-Apr79(2):151-64. doi: 10.4103/0378-6323.107629.

• Venom anaphylaxis – immunotherapy pharmalgen; NICE Technology appraisal guidance, February 2012

1. Insect bites and stings; NICE CKS, September 2020 (UK access only)

2. Przybilla B, Rueff F; Insect stings: clinical features and management. Dtsch Arztebl Int. 2012 Mar109(13):238-48. doi: 10.3238/arztebl.2012.0238. Epub 2012 Mar 30.

3. Peres G, Yugar LBT, Haddad Junior V; Breakfast, lunch, and dinner sign: a hallmark of flea and bedbug bites. An Bras Dermatol. 2018 Sep-Oct93(5):759-760. doi: 10.1590/abd1806-4841.20187384.

4. Insect bites and stings: antimicrobial prescribing; NICE Guidance (September 2020)

5. Cellulitis and erysipelas: antimicrobial prescribing; NICE Guidance (September 2019)

6. Severino M, Bonadonna P, Passalacqua G; Large local reactions from stinging insects: from epidemiology to management. Curr Opin Allergy Clin Immunol. 2009 Aug9(4):334-7.

7. Koterba AP, Greenberger PA; Chapter 4: Stinging insect allergy and venom immunotherapy. Allergy Asthma Proc. 2012 May-Jun33 Suppl 1:12-4.

8. Tracy JM, Lewis EJ, Demain JG; Insect anaphylaxis: addressing clinical challenges. Curr Opin Allergy Clin Immunol. 2011 Aug11(4):332-6.

9. Demain JG, Minaei AA, Tracy JM; Anaphylaxis and insect allergy. Curr Opin Allergy Clin Immunol. 2010 Aug10(4):318-22.

10. Diagnosis and management of hymenoptera venom allergy – guidelines; British Society for Allergy and Clinical Immunology (2011)

11. Boyle RJ, Elremeli M, Hockenhull J, et al; Venom immunotherapy for preventing allergic reactions to insect stings. Cochrane Database Syst Rev. 2012 Oct 1710:CD008838. doi: 10.1002/14651858.CD008838.pub2.

12. Radolf JD, Caimano MJ, Stevenson B, et al; Of ticks, mice and men: understanding the dual-host lifestyle of Lyme disease spirochaetes. Nat Rev Microbiol. 2012 Jan 910(2):87-99. doi: 10.1038/nrmicro2714.

Cellulitis and other bacterial skin infections

See also

Antibiotics

Invasive group A streptococcal infections: management of household contacts

Periorbital and orbital cellulitis

Sepsis

Key points

1. Cellulitis is a spreading infection of the skin extending to involve the subcutaneous tissues. Many conditions present similarly to cellulitis — always consider differential diagnoses
2. The typical presenting features of all skin infections include soft tissue redness, warmth and swelling, but other features are variable
3. Allergic reactions and contact dermatitis are frequently misdiagnosed as cellulitis. If there is itch and no tenderness, cellulitis is unlikely

Background

Cellulitis

• The most common causes are Group A streptococcus (GAS) and Staphylococcus aureus. Predisposing factors include skin abrasions, lacerations, burns, eczematous skin, chickenpox, etc. although the portal of entry of organisms is often not seen

Impetigo (commonly called “school sores”) 

• Highly contagious infection of the epidermis, particularly common in young children Causative organisms are GAS and S. aureus
• May be associated with scabies

Staphylococcal scalded skin syndrome (SSSS) 

• Blistering skin disorder induced by the exfoliative (epidermolytic) toxins of S. aureus. Primarily affects neonates and young children

Necrotising fasciitis 

• Rapidly progressive soft tissue infection characterised by necrosis of subcutaneous tissue
• Causative organisms include GAS, S. aureus, anaerobes and is often polymicrobial
• It causes severe illness with a high mortality rate (~25%)
• Recent infection with varicella is a risk factor

Cellulitis associated with water borne organisms

• Aeromonas species (fresh or brackish water, and mud)
• Mycobacterium marinum (fish tanks)
• Vibrio species (salt or brackish water)
• S. aureus, including MRSA
• GAS (coral cuts)

Infected animal/human bites

• Caused by different organisms and often require different treatment
• Other bites are discussed elsewhere, see
  Snakebite,
  Spider bite – big black spider,
  Spider bite – red-back spider

There are many other forms of skin infection that are not covered in this guideline

Assessment

Typical presentation of all skin infections

• Soft tissue redness
• Warmth and swelling
• Pain/tenderness

Mild Cellulitis

• Features above
• No systemic features
• No significant co-morbidities 

Moderate Cellulitis

• Features above with moderate swelling and tenderness
• Systemic features (eg fever, tachycardia)

Severe Cellulitis

• Features above with severe swelling or tenderness
• Large body surface area involved (eg larger than the patient’s handprint)
• Marked systemic features (eg fever or hypothermia, tachycardia, tachypnoea, altered conscious state, unwell appearance, hypotension — this is a late sign). See Sepsis

Features suggestive of necrotising fasciitis include:

• severe pain out of keeping with apparent severity of infection
• rapid progression
• marked systemic features (eg high fever with rigors, tachycardia, tachypnoea, hypotension, confusion, vomiting). See Sepsis

Red flags

• Abscess or suppuration
• Animal or human bite
• Deep structure involvement
• Foreign body
• Immunosuppression
• Lymphangitis
• MRSA infection
• Multiple comorbidities
• Periorbital/facial/hand involvement
• Varicella associated infection

Differential Diagnosis

Large local reactions to insect bites are a common mimic of cellulitis. Features include:

• a punctum at the site
• itch as a prominent feature
• redness and induration, but rarely pain

Management

Investigations

• Swab for Gram stain (charcoal / gel / bacterial transport swab and slide) and culture if discharge present
• Blood culture is not useful in mild/moderate cellulitis
• Consider imaging (eg ultrasound) if abscess, deep infection or foreign body suspected

Treatment

• Manage
  sepsis if features present
• Manage source if identifiable — ie remove foreign body, drain abscess
• For ongoing management refer to flowchart below

Summary of antibiotic therapy

Antimicrobial recommendations may vary according to local antimicrobial susceptibility patterns; please refer to local guidelines

Cellulitis frequently looks worse after 24 hours of treatment; consider waiting 48 hours to change therapies

Young, unvaccinated children are at risk of
Haemophilus influenzae type B (Hib)

*Indications for prophylactic antibiotics in a animal/human bite

• Presentation delayed by >8 hours
• Puncture wound unable to be adequately debrided
• Bite on hands, feet, face
• Involves deep tissues (eg bones, joints, tendons)
• Involves an open fracture
• Immunocompromised patient
• Cat bites

Suggested antibiotic therapy where MRSA is suspected

Antimicrobial recommendations may vary according to local antimicrobial susceptibility patterns; please refer to
local guidelines

Risk factors for MRSA infection 

• Residence in an area with high prevalence of MRSA, eg Northern Territory, remote communities in northern Queensland
• Previous colonisation or infection with MRSA (particularly recent)
• Aboriginal and Torres Strait Islander or Pacific Islander child

Consider consultation with local paediatric team when

• No improvement or deterioration after 24–48 hours of therapy
• Deep abscess or necrotising fasciitis suspected — consider surgical opinion 

Consider transfer when 

Child requires care above the level of comfort of local hospital

For emergency advice and paediatric or neonatal ICU transfers, see Retrieval Services

Consider discharge when 

Able to tolerate oral antibiotics

Parent Information

Cellulitis

Impetigo

Staphylococcal infections

Bleach Baths

Last Updated March 2020

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90,000 allergies, infection or insect bites?

Baby Rash: Allergy, Infection, or Insect Bites?

03/22/2020

Insect bites

In late spring, summer and early autumn, children often suffer from insect bites. The skin is covered with bumps and spots. Usually only exposed areas of the body and face are affected. Most often, the rash is accompanied by itching. The general condition and well-being of the child does not change.

What does it look like?

What to do?

Allergy ointments or gels are recommended. If the baby combs the bites, it is necessary to lubricate them with brilliant green to prevent the accumulation of bacterial infection and inflammation.

Allergic rash

Activated after eating new foods – mussels, shrimps, exotic berries and fruits, cow’s milk, eggs. It appears in the form of intensely itchy pink and red spots that tend to coalesce. The state of health may worsen, especially with severe allergies. The baby is lethargic or, on the contrary, overly excited. Sleep and appetite are disturbed, diarrhea and vomiting are possible.

What does it look like?

What to do?

Prescribe a sparing hypoallergenic diet, antihistamines. As an addition – drugs that bind and remove food allergens from the body – enterosorbents. If irritation is caused by contact with detergent or cosmetics, eliminate the allergen.

Prickly heat

Usually manifests itself with the onset of heat. Beige-pink pimples are located very close to each other. Most of the rashes are in the upper chest, on the shoulders and neck. Sometimes tiny blisters may come out. They don’t bother the child.

What does it look like?

What to do?

Ventilate the skin regularly and monitor the room temperature – it should be +20°C. To remove excess moisture, you need to use powder. Reddened skin should not be lubricated with cream. Clothing should be made only from natural materials.

Urticaria

Pale, band-like, intensely itchy swellings. Pink blisters may appear, which become covered with a red bloody crust when combed. The baby sleeps and eats badly. Over time, intradermal edema subsides, and swelling disappears without a trace. Urticaria can be caused by infections, allergies, or physical irritants.

What does it look like?

What to do?

In agreement with the doctor, antihistamines are used.

Chickenpox

Before the rash appears, the child complains of headache and malaise. He may have a runny nose and a slight fever. Sometimes they misdiagnose SARS. At first, only a few spots are noticeable, every day there are more and more of them.

In severe cases, the rash affects the mucous membranes. After a couple of days, the spots turn into tubercles filled with transparent contents. Then they burst, forming crusts. The rash with chickenpox is accompanied by itching.

What does it look like?

What to do?

Treat with brilliant green.