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 (animal 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 (animal 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
- 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
- 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
Department of Emergency Medicine
University of Florida
TM declares that he has no competing interests.
Tom Morrissey would like to gratefully acknowledge the assistance of Richard Vetter (MS) from the Department of Urban Entomology at the University of California.
Allergist and Immunologist
Jacobs Ramirez and Freeman Allergy & Immunology
TMF is an author of a number of references cited in this topic.
Associate Medical Director
Consultant Emergency Medicine
Guy's and St Thomas' NHS Foundation Trust
Clinical Lead and Consultant
Accident Emergency Medicine
St Thomas' Hospital
AP declares that he has no competing interests.
Chairman and Professor
Department of Medicine
Professor of Pediatrics
Billy S. Guyton Distinguished Professor
University of Mississippi Medical Center
RD is an author of a reference cited in this topic.
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