From the Guidelines
An arthropod-mediated hypersensitivity reaction is an allergic response that occurs when a person's immune system overreacts to proteins in the saliva, venom, or body parts of arthropods such as insects, spiders, mites, and ticks, typically manifesting as localized skin symptoms or systemic reactions ranging from widespread hives to life-threatening anaphylaxis. These reactions can be caused by various arthropods, including insects like honeybees, yellow jackets, hornets, wasps, and fire ants, as well as spiders, mites, and ticks 1. The immune system produces IgE antibodies against arthropod proteins, triggering mast cell degranulation and release of inflammatory mediators like histamine when re-exposure occurs.
Symptoms and Diagnosis
Symptoms of arthropod-mediated hypersensitivity reactions can range from mild to severe and include:
- Localized skin symptoms such as redness, swelling, itching, and hives at the site of contact or bite
- Systemic reactions, including urticaria and angioedema, bronchospasm, edema of the large airway, hypotension, or other clinical manifestations of anaphylaxis 1
- Life-threatening anaphylaxis characterized by difficulty breathing, throat swelling, and cardiovascular collapse
Diagnosis is typically confirmed by a history of a systemic reaction to an insect sting, and testing for specific IgE antibodies to stinging insects, such as skin testing or in vitro testing 1.
Management and Prevention
Management of arthropod-mediated hypersensitivity reactions depends on the severity of the reaction. Mild reactions can be treated with:
- Oral antihistamines like diphenhydramine (25-50mg every 4-6 hours) or cetirizine (10mg daily)
- Topical corticosteroids such as hydrocortisone 1% cream applied 2-3 times daily
- Cold compresses
Severe reactions require immediate epinephrine (0.3-0.5mg intramuscularly for adults, 0.15mg for small children) and emergency medical attention. Prevention strategies include:
- Using insect repellents containing DEET or picaridin
- Wearing protective clothing
- Avoiding known habitats of problematic arthropods
- Carrying epinephrine for emergency self-administration and being instructed in its appropriate indications and administration
- Undergoing testing for specific IgE antibodies to stinging insects
- Considering immunotherapy (with insect venom or fire ant whole-body extract) if test results for specific IgE antibodies are positive 1.
From the Research
Definition and Causes
- An arthropod-mediated hypersensitivity reaction refers to an allergic reaction caused by the bites or stings of arthropods, such as insects, spiders, and ticks 2, 3.
- These reactions can range from mild to severe and can be caused by a variety of arthropod species, including fleas, bedbugs, mosquitoes, and bees 2, 4.
Symptoms and Diagnosis
- Symptoms of arthropod-mediated hypersensitivity reactions can include urticarial wheals, papular reactions, bullous or hemorrhagic reactions, and systemic reactions such as anaphylaxis 3, 5.
- Diagnosis of these reactions can be challenging due to the diversity of symptoms and the lack of standardization of extracts for skin testing and specific IgE determination 3, 6.
Types of Reactions
- Localized reactions, such as urticarial wheals and papular reactions, are the most common type of arthropod-mediated hypersensitivity reaction 3.
- Systemic reactions, such as anaphylaxis, are less common but can be life-threatening 3, 5.
- Alpha-gal syndrome (AGS) is a type of arthropod-mediated hypersensitivity reaction associated with anti-alpha-gal IgE antibody titres 5.
Treatment and Prevention
- Treatment of arthropod-mediated hypersensitivity reactions typically involves avoidance of the offending arthropod and the use of emergency drugs such as epinephrine 3.
- Recombinant allergens and peptides have been developed as diagnostic and therapeutic reagents for arthropod allergies, offering a more specific and effective approach to diagnosis and treatment 6.