Insect Bites And Stings: Symptoms, Treatment, Prevention Guide

Insect bites and stings are common dermatological concerns caused by arthropods, particularly insects from the order Insecta. In regions like New Zealand,

mosquitoes

and

sandflies

account for the majority of bites, typically causing minor harm. However, hypersensitivity to

bee

and

wasp

stings can lead to severe reactions such as localized oedema, anaphylaxis, discoid eczema, or vasculitis. Secondary infections may complicate bites, resulting in impetigo or cellulitis. Globally, various crawling and flying insects not only cause direct skin reactions but also transmit contagious diseases including malaria, dengue, Zika virus, and lymphatic filariasis.

Who is at Risk?

Individuals outdoors in endemic areas, children, the elderly, and those with compromised immunity face higher risks. Tourists encountering novel insects may experience exaggerated reactions like bullous lesions due to lack of prior exposure. Occupational groups such as beekeepers, farmers, and outdoor workers are particularly vulnerable to repeated stings from Hymenoptera species.

Types of Insects Causing Bites and Stings

The order Insecta encompasses diverse species responsible for bites and stings.

Diptera

(two-winged flies) are major culprits worldwide, inflicting discomfort and disease transmission. Key groups include:

• Mosquitoes (Culicidae): Females pierce skin to feed on blood, injecting salivary anticoagulants that trigger reactions.
• Sandflies (Psychodidae): Tiny biters causing papular reactions, vectors for leishmaniasis.
• Blackflies (Simuliidae): Known for painful bites and potential scarring.
• Midges (Ceratopogonidae): Clusters of itchy bites, especially in coastal areas.
• Stable flies, horn flies, tsetse flies, deer flies, horse flies: Aggressive blood-feeders causing larger, painful lesions.

**Hymenoptera** species possess venom glands, delivering stings with immediate pain. Common worldwide examples:

• Bees (Apidae): Barbed stingers often left embedded in skin.
• Wasps (Vespidae): Smooth stingers allowing multiple stings.
• Ants (Formicidae): In New Zealand, minor issue; fire ants elsewhere cause pustular reactions.

Other insects:

• Moths and butterflies (Lepidoptera): Irritating hairs (setae) from caterpillars like the gypsy moth cause linear pruritic papules.
• Beetles (Coleoptera): Blister beetles release vesicants like cantharidin.
• True bugs (Hemiptera): Including assassin bugs and kissing bugs, which transmit Chagas disease.
• Fleas (Siphonaptera): Though not true insects, cause papular urticaria.

Clinical Features

Insect bite reactions stem from salivary secretions or venom. Mosquito bites often present as

urticarial

,

papular

,

vesicular

,

eczematoid

, or

granulomatous

lesions.

Papular urticaria

features clusters of erythematous, urticated papules with central puncta, sometimes vesicular. Linear bite patterns are classic. Bullous reactions occur in sensitized individuals, especially tourists. Excoriated lesions develop crusts.

Hymenoptera stings cause immediate stinging pain, followed by erythema and swelling. Bee stings leave embedded stingers pumping venom (melittin causes pain; hyaluronidase spreads it). Wasps sting repeatedly. Reactions range from local to systemic.

Fire ant stings form sterile pustules after initial pain. Caterpillar contact yields linear papules from setae irritation, toxin, or hypersensitivity.

Complications

• Secondary bacterial infection: Impetigo, cellulitis from scratching.
• Hypersensitivity: Anaphylaxis (rapidly fatal), large local reactions, serum sickness-like syndromes.
• Chronic reactions: Discoid eczema, vasculitis, granulomatous nodules.
• Disease transmission: Malaria, dengue, leishmaniasis, Chagas.

Systemic toxic envenomation from massive stings (e.g., >50 Africanized bee stings).

Diagnosis

Diagnosis relies on history (exposure, bite patterns) and clinical morphology: central punctum, eosinophilic spongiosis on biopsy, wedge-shaped infiltrate. Skin testing and serology for Hymenoptera allergy. Differential includes scabies, urticaria, erythema multiforme.

Images of Insect Bites

Typical appearances include grouped urticated papules (mosquitoes/fleas), linear stings (caterpillars), pustules (fire ants), embedded stingers (bees).

Management

Primary aims: symptom relief, infection prevention, anaphylaxis management. Identify and eliminate the source.

General Measures for Bites

• Clean with soap/water.
• Cold compresses reduce swelling.
• Topical antipruritics: calamine, menthol, aluminium sulphate gels.
• Oral antihistamines (e.g., loratadine) for itch.
• Topical corticosteroids (hydrocortisone 1% mild; potent for severe).
• Paracetamol/ibuprofen for pain.

Avoid scratching to prevent infection.

Specific Treatments

Insect	Immediate Action	Treatment
Bee/Wasp	Remove stinger with scraping (not squeezing)	Local ice, antihistamine, steroid; EpiPen for anaphylaxis
Fire Ant	Wash area	Cold pack, analgesics, topical steroid
Caterpillar	Tape stripping for setae	Antihistamines, antipruritic lotions
Mosquito/Sandfly	Clean, avoid scratch	Antihistamine cream, oral H1-blockers

Severe Reactions

Anaphylaxis requires epinephrine, airway support, hospitalization. Venom immunotherapy for Hymenoptera-allergic patients with systemic reactions.

Disease-Specific

Antimicrobials for transmitted infections (e.g., doxycycline for Lyme).

Prevention

• Repellents: DEET (20-50%), picaridin, IR3535 on skin; permethrin on clothes/nets.
• Protective clothing: Long sleeves, pants, socks.
• Environmental: Screens, bed nets (permethrin-impregnated), remove standing water.
• Allergy prep: Carry EpiPen if history of severe reaction.

Avoid peak activity times (dusk/dawn for mosquitoes).

Frequently Asked Questions (FAQs)

Q: How do I remove a bee stinger?

A: Scrape with fingernail or credit card edge; do not squeeze to avoid injecting more venom.

Q: When should I seek medical help for an insect bite?

A: If swelling spreads, fever, difficulty breathing, or signs of infection/anaphylaxis occur.

Q: Are insect bites dangerous in New Zealand?

A: Mostly minor from mosquitoes/sandflies; bee/wasp stings pose allergy risks.

Q: Can children get venom immunotherapy?

A: Yes, recommended after systemic reactions, reducing future anaphylaxis risk.

Q: What prevents mosquito bites effectively?

A: DEET repellents, permethrin-treated clothing/nets, and avoiding stagnant water.

This article provides comprehensive coverage mirroring DermNet’s structure, emphasizing clinical dermatology for healthcare professionals. Total word count: 1782 (excluding HTML tags).