Insect Bites and Stings (Mosquitos)

4 Sept

Insects bite by puncturing the skin with piercing mouthparts usually to feed (including mosquitos. An insect sting is defined by the use of another body part of the insect to pierce the skin and inject venom. Mosquitoes bites derive from females using a 6 needle- like mouthpiece; preferring exposed skin mainly seen in the summer months. Mosquitoes are vectors (which carry pathogens), therefore their bites can transmit diseases such as malaria (which are vector-borne)

- In the UK, insect stings are the second most common cause of anaphylaxis outside of medical settings [1]
- One study conducted in England and Wales (GPs) 1999 - 2003; the highest incidence rate was in females aged 15 or older (7.0 per 100 000) and the lowest incidence rate being 3.2 per 100 000 in males aged 15 years or older. [2]
- Certain racial and ethnic groups might be more affected due to the regions they inhabit.
- In areas where vector-borne diseases like malaria or dengue fever are prevalent. For example, African and South Asian populations are more exposed to malaria due to the geographical presence of the disease. [3]
- Insect feeding or a defence reaction
- Mosquito eggs are laid in stagnant water (increased risk after floods/ tsunamis) [1]
Medical Student
- Mosquito Feeding Mechanism: Uses its proboscis, with serrated maxillae cutting the skin and mandibles holding tissue apart, to locate and access blood vessels via the labrum.
- Salivary Injection: Injects saliva containing anticoagulants, vasodilators, and enzymes that facilitate feeding.
- Immune Recognition: Saliva proteins are recognised as foreign, triggering an innate immune response.
- Histamine Response: Histamine increases vascular permeability, leading to classic signs of inflammation (redness, swelling, itch).
- Immune Phases & Sequelae: Immediate (wheal and flare) and delayed (T-cell-mediated) responses can occur; excessive scratching or skin tone may influence risk of post-inflammatory hyperpigmentation or scarring.
Patient
- How Mosquitoes Bite: Mosquitoes use a thin, sharp mouthpart to pierce your skin and find a blood vessel.
- Why They Inject Saliva: Their saliva helps stop your blood from clotting and makes it easier for them to feed.
- Your Body’s Reaction: Your immune system sees the saliva as foreign and reacts to it.
- What You Feel: The reaction causes a small bump, redness, swelling, and itchiness, this is your body trying to fight off the saliva.
- After Effects: If you scratch too much, or if you have darker skin, the bite may leave a dark mark or scar as it heals.
- Time period: Some are most active at dawn and dusk, while others bite throughout the night or even during the day.
- Lifestyle factors: occupation and hiking which increases exposure to the regions which higher rates of tick infestation
- Increased skin exposure
- Carbon Dioxide: Mosquitoes are attracted to carbon dioxide (CO2 can be detected from over 100 feet away)
- Blood type: Mosquitoes are particularly drawn to people with O blood type (anecdotal, no significant proof) [5]
- There is some evidence to suggest that darker skin may have different reactions to bites
- Potentially leading to less noticeable or different types of bite marks compared to lighter skin. However, this varies significantly among individuals.
- Painless bite
- Wheals and papules are round and have a central bite mark
- Erythema (redness)
- Pruritus (itchiness)
- Oedema (swelling) [6]
- Skin-coloured, violet, or brown on darker skin
- After the bites heal, they may leave brown marks on your skin [7]
- Small blisters
- Dark spots that look like bruises
- In severe cases; Low-grade fever and swollen lymph nodes [8]
- Clinical examination of appearance and history of symptoms
- Investigations for severe reactions to insect bites or stings should be carried out in secondary care. [9]
- Trauma to the skin
- Other stings from plants
- Skin infection such as abscess, folliculitis or cellulitis.
- Skin tumours such as basal cell carcinoma, squamous cell carcinoma, melanoma and Kaposi’s sarcoma
- Contact dermatitis
- Chicken pox
- Urticaria [10]
Medical student
- Clean the Area: Wash the bite area thoroughly with soap and water to reduce the risk of infection.
- Apply Cold Compress: Place a cloth soaked in cold water over the bite to reduce swelling and soothe the area.
- Pain Management: If the bite is painful or swollen, recommend an analgesic such as paracetamol or ibuprofen to alleviate discomfort.
- Reduce Swelling: Administer an oral antihistamine (such as chlorphenamine) or topical corticosteroids (such as hydrocortisone 1%) to help reduce swelling and alleviate itching.
- Topical Treatment: Topical antipruritics (such as crotamitin), topical antihistamines and topical anaesthetics sold over-the-counter are of uncertain value in the treatment of insect bites and may themselves cause irritant skin reactions.
General Precautions:
- Wear long-sleeved clothing, trousers, and socks to cover exposed skin.
- Avoid walking barefoot or in sandals outside.
- Refrain from using strongly scented products like perfumes, soaps, and shampoos.
- Stay away from areas with a high risk of insect stings, such as places with food, drink, or rubbish bins.
- Be cautious when drinking from opaque containers outdoors.
- Have insect nests near your home removed by professionals.
- Keep approved insecticides for stinging insects on hand for emergencies, but note that insect repellents are ineffective against these insects.
If in Tick-Infested Areas:
- Cover exposed skin with long sleeves and tuck trousers into socks.
- Light-colored clothing helps spot ticks more easily.
- Use insect repellent.
- Regularly inspect skin, particularly children’s heads, scalps, and necks, for ticks. Also, check clothes and pets for ticks.
Patients
- Clean the bite: Gently wash the area with soap and water to help prevent infection.
- Cool it down: Use a cloth soaked in cold water and place it on the bite to help with swelling and soothe the itch.
- Take something for the pain: If it hurts or swells, you can take paracetamol or ibuprofen.
- Ease the itching and swelling: You can try an allergy tablet (like chlorphenamine) or use a mild cream (like hydrocortisone) to help reduce itchiness and swelling.
- Be careful with creams: Some creams you can buy at the pharmacy for itching or pain might not work well and could make your skin more irritated.
How to Avoid Getting Bitten or Stung:
- Cover your skin: Wear long sleeves, trousers, and socks when you're outside.
- Protect your feet: Don’t walk outside barefoot or in sandals.
- Go scent-free: Avoid strong-smelling perfumes, soaps, or shampoos that attract insects.
- Watch where you are: Stay away from food, drinks, or rubbish bins where insects gather. Be careful with cans or bottles outdoors.
- Remove nests: If you see insect nests near your home, ask a professional to remove them.
- Have sprays ready: Keep insect sprays that are made for stinging insects nearby. Regular repellents might not work for these types.
If You're in an Area With Ticks:
- Wear long sleeves and tuck your trousers into your socks.
- It’s easier to spot ticks on light clothing.
- Choose a repellent that works against ticks.
- Look at your skin carefully, especially on children’s heads and necks. Also check your clothes and pets.
- Scratching the bite can introduce bacteria into the skin, leading to secondary bacterial infections such as impetigo.
- Some individuals may develop more severe allergic reactions to mosquito bites, known as "skeeter syndrome."
- This condition involves intense swelling, pain, and sometimes systemic symptoms like fever.
- Mosquitoes can transmit various pathogens through their bites, including malaria, dengue fever, Zika virus, and West Nile virus.
- When a mosquito carrying a pathogen bites, the pathogen is introduced into the bloodstream along with the saliva, leading to infection. [6]
- Mosquitos are only attracted to ‘sugary’ blood in people with conditions like diabetes
- Mosquitoes transmit HIV
- All mosquitoes bite humans
- Citronella candles repel mosquitoes
- Perfumes and lotions repel mosquitos [12]
- What can I do to stop the itch?
- How do I know if the bite becomes infected?
- What are the side effects of the medication prescribed?
- How often should I take my cream/ oral medication?
- What can I do to prevent being bitten again?
- Fit For Travel
- GOV.UK- Mosquito bite avoidance
- CDC- Travelers' HealthAvoid bug bites
[1] A Systematic Review of the Clinical Effectiveness and Cost-Effectiveness of Pharmalgen® for the Treatment of Bee and Wasp Venom Allergy.
[2] The association between impetigo, insect bites and air temperature: a retrospective 5-year study (1999-2003)
[3] Global Change and Human Vulnerability to Vector-Borne Diseases
[4] Beat the bite: pathophysiology and management of itch in mosquito bites
[5] Are You Prone to Mosquito Bites?
[6] Mosquito Bites
[7] Bedbug Bites vs. Mosquito Bites: How to Tell Insect Bites Apart (With Pictures)
[8] About Mosquito Bites
[9] How should I assess a person with a suspected insect bite or sting?
[10] NICE: Differential diagnosis
[11] CDC: Avoid Bug Bites
[12] Mosquito Facts and Myths