Insect bite/sting

Diagnosis of Insect Bites

  • Clinical Evaluation:
    • History: When and where the bite occurred, activities at the time, outdoor exposure, and any known insect contact.
    • Symptoms: Pain, itching, redness, swelling, or systemic symptoms.
    • Physical Exam: Look for local reactions (erythema, swelling, vesicles), patterns of bites (single or multiple, linear or grouped), and signs of infection or allergic reaction.
  • Characteristic Features of Some Bites:
    • Mosquito Bites: Small, puffy, pink bumps that often become itchy.
    • Flea Bites: Small red bumps, often in groups of three or four or a straight line.
    • Bedbug Bites: Red and itchy bumps, often in a line or grouped, usually on the face, neck, arms, and hands.
    • Tick Bites: Single bite with or without the tick still attached; may develop a bullseye rash.
    • Spider Bites: Can vary widely from small local reactions to significant necrosis, depending on the species.

Differential Diagnosis

  • Skin Infections: Bacterial (impetigo, cellulitis), viral (herpes simplex), or fungal infections.
  • Allergic Reactions: To substances other than insect bites.
  • Arthropod Assault: Scabies, lice.
  • Dermatitis: Contact, atopic, or other types of dermatitis.
  • Papular Urticaria: Hypersensitivity to insect bites, leading to a chronic or recurrent pattern of lesions.
  • Drug Reactions: Some drugs can cause skin eruptions that mimic insect bites.
  • Vascular Lesions: Vasculitis or thrombophlebitis can sometimes look similar to insect bites.

Management of Insect Bites

  • General Measures:
    • Cleaning: Wash the area with soap and water.
    • Cold Compresses: Reduce swelling and pain.
    • Topical Creams: Calamine lotion or over-the-counter hydrocortisone cream can relieve itching.
    • Antihistamines: Oral antihistamines may help relieve itching and swelling.
    • Avoid Scratching: To prevent secondary infection and promote healing.
  • For Specific Insects:
  • Tick Bites:
    • Kill the tick using liquid nitrogen or ether spray
    • Allow the tick to fall off (or Remove the tick with care not to inject more saliva)
    • Observe for signs of tick-borne illnesses.
  • Bee Stings:
    • Remove the stinger by scraping across the skin to avoid squeezing the venom sac
    • observe for signs of an allergic reaction.
  • Spider Bites: Some, like the black widow or brown recluse spider bites, may require medical treatment.
  • Preventing Infection:
    • Antiseptics: Apply to prevent secondary bacterial infection.
    • Antibiotics: Only if there is evidence of secondary infection.
  • Severe Reactions:
    • Allergic Reactions: Monitor for signs of anaphylaxis, such as difficulty breathing, swelling of the lips or throat, rapid pulse, or dizziness. 
    • Anaphylaxis: This is a medical emergency. Treat with adrenaline 0.5mg IM stat every 5/60 as required

Follow-Up and Prevention

  • Monitoring:
    • Follow-Up: Check for signs of infection or an allergic reaction over the next few days.
  • Preventive Measures:
    • Repellents: Use insect repellent when outdoors.
    • Clothing: Wear long sleeves and pants when in wooded areas or where insects are common.
    • Environmental Control: Reduce standing water and other breeding sites for mosquitoes.

When to Seek Medical Attention

  • If there is a severe allergic reaction or any signs of anaphylaxis.
  • If the bite site becomes increasingly red, warm, swollen, or painful, as these are signs of secondary bacterial infection.
  • If a tick bite is followed by flu-like symptoms, a rash, or joint pain.
  • If the patient has a known severe allergy to insect bites or stings, they should have an epinephrine auto-injector available and know how to use it.