Reactions range from local irritation and mild swelling to gross oral swelling and difficulty in breathing.
Treatment is usually entirely supportive, aimed at alleviating immune reactions. Severe reactions and anaphylaxis require immediate intervention to maintain airway patency and prevent cardiovascular collapse. Injected adrenaline (epinephrine) is the mainstay treatment of severe reactions.
Fatal spider bites are exceedingly rare. Most spider bites can be treated with supportive care.
Guidelines are mainly based on clinical experience and expert consensus, owing to the variability and unpredictability of reactions.
There is a risk of late-phase (delayed) anaphylactic reactions.
Primary care physicians should be notified of severe reactions involving their patients.
The term 'insect' refers to a distinct taxonomic class. However, it is used generically throughout this topic to represent a multitude of bugs, including arachnids. Encounters with insects or arachnids can result in bites or stings.
Bites stem from puncture with a proboscis (head appendage) or fangs, or from chewing with mouth parts. Depending on the source, bites range from being immediately painful to completely unfelt, and health consequences may be caused by local trauma, the injection of various substances (irritants, venoms, poisons, toxins, anaesthetics, enzymes, anticoagulants), disease transmission, secondary infection, or systemic allergic reactions (rare).
Stings from insects are administered from ovipositors (organs used for laying eggs that may also inject various noxious substances) or modified ovipositors (e.g., barbed stingers of bees and wasps). Stings are almost always immediately painful. Reactions range from local irritation and swelling to life-threatening anaphylactic reactions.
History and exam
Key diagnostic factors
- presence of risk factors
- witnessed bite/sting
- local oedema
- local pain
- local warmth
- local markings
- wheal and flare
- skin pallor
- signs of airway compromise
- oropharyngeal oedema
- irregular pulse
- skin flushing
- altered alertness
Other diagnostic factors
- bullseye-shaped rash
- rash on palms and soles
- linear raised rash
- muscle cramp
- paraesthesia and/or fasciculations
- generalised pain
- abdominal pain
- history of immunocompromised state
- history of cardiovascular disease
- occupational or recreational exposure to insects
- geographical exposure to insects
- previous history of anaphylactic (or anaphylactoid) response
1st investigations to order
- clinical diagnosis
Investigations to consider
- serum tryptase
- sensitivity testing
secondary infection: immunocompetent; low MRSA risk
- Periorbital and orbital cellulitis
- Anaphylaxis - a 2020 practice parameter update, systematic review, and Grading of Recommendations, Assessment, Development and Evaluation (GRADE)
- Insect bites and stings: antimicrobial prescribing
Insect bites and stingsMore Patient leaflets
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