II. Pathophysiology: Arthropod types
- Arachnids (8 legs)
- Spiders
- See Spider Bite
- Black Widow Spider (Lactodectus mactans)
- Brown Recluse Spider (Loxosceles reclusa)
- Precautions
- "Spider Bites" are typically not due to Spiders, but rather other causes (e.g. MRSA Cellulitis)
- Most Spider Bites are benign (not black widow or brown recluse)
- Need only minimal local therapy (Wound Cleansing, cold therapy)
- Mites
- Scorpions
- Ticks
- See Tick Bite
- See Vector Borne Disease
- Spiders
- Insects (6 legs)
- Diptera (2-winged Insects)
- Siphonaptera
- Fleas
- Hemiptera ("true bugs")
- Psocodea
- Hymenoptera (includes Stinging Insects)
- See Stinging Insect Bite
- Apidae (Bees)
- Honey bees
- Bumble bees
- Vespidae
- Wasps
- Yellow Jackets
- Hornets
- Formicidae (Stinging Ants)
III. Signs
- Most "Spider Bites" are due to some other cause
- Pruritic, Red Papules
- Typical Insect Bite (e.g. Mosquito Bite or biting midge such as no-see-ums, Sand Fly)
- Pruritic welts along constrictive clothing lines (waist band or sock line)
- Clustered or linear Papules at the ankles
IV. Differential Diagnosis: Insect Bite Reaction
- See Annular Lesion
- See Stinging Insect Reaction
- Folliculitis
- Impetigo
- Cellulitis
- Shingles
- Contact Dermatitis
-
Erythema Migrans
- Most Insect Bite reactions are localized (typically <2.5 to 5 cm in size) and resolves in first 48 hours
- Erythema Migrans insyead, continues to expand at >48 hours to diameters often >10 cm
-
Erythema Multiforme
- Multiple target lesions each typically <2 cm diameter
-
Granuloma Annulare
- Scaling erythematous lesions with central clearing (esp. hands and feet)
-
Methicillin Resistant Staphylococcus Aureus (MRSA)
- Lesions with necrotic central eschar
- Tinea Corporis
- Urticaria
V. Complications
- Anaphylaxis or other serious Allergic Reaction
- Papular Urticaria
- Vector Borne Disease (e.g. Lyme Disease with Erythema Migrans)
-
Cellulitis
- Inflammation out of proportion to Insect Bite
- Regional Lymphadenopathy
- Ascending lymphangitis
VI. Management: General
- Remove Stinger with forceps (avoid pinching the Stinger gland)
- Apply ice pack for 10-20 minutes per hour for 3 hours
- Contraindicated in Tarantula Bite
- Treat itch symptomatically
- Oral Benadryl for nighttime itch, Zyrtec for daytime itch
- Cool compresses
- Oral Analgesics (e.g. Acetaminophen or NSAIDs)
- Anti-irritant agents (e.g. sarna)
- Protective agents (e.g. calamine)
- Topical Corticosteroids (low potency such as 1% Hydrocortisone, brief use) may be considered
- Avoid topical Antihistamines (e.g. topical Benadryl) due to Contact Dermatitis risk
VII. Management: Acute Allergic Reaction
- See Anaphylaxis
- See Stinging Insect Allergy
- Prescribe Epi-Pen for emergency use for those with Anaphylaxis history
VIII. Management: Suspected Cellulitis
- See Cellulitis for Antibiotic selection
- Tetanus Prophylaxis
IX. Prevention
- See Prevention of Vector-borne Infection
- Check clothes for Insects before donning
- Avoid times of peak Insect activity (dawn and dusk)
- Avoid habitats
- Woodpiles
- Crawl spaces
- Corners of buildings
- Standing water
- Dense vegetation
- Dress for working outdoors
- Keep skin covered by clothing
- Wear gloves
- Shirt tucked into pants
- Pants tucked into socks
- Wear a hat and high collar
- Avoid loose clothing
- Avoid Insect attractants
- Avoid bright colors (wear light colored clothing)
- Avoid perfumes
- Keep skin covered by clothing
-
Insect Repellents
- See Insect Repellent
- DEET (<30% is safe in young children)
- Permethrin (Elimite, Nix) on clothes
- Ticks
X. References
- Norris (1998) Physician and Sports Med 26(7):47-58
- Herness (2022) Am Fam Physician 106(2): 137-47 [PubMed]
- Juckett (2013) Am Fam Physician 88(12): 841-7 [PubMed]
- Kemp (1998) Postgrad Med 103(6):88-106 [PubMed]