What Are Insect Bites? How To Treat Insect Bites

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Main Category: Dermatology
Also Included In: Tropical Diseases
Article Date: 16 Dec 2009 - 5:00 PDT


Insect bites are puncture wounds or lacerations made by insects. An insect may bite when it is agitated and defends itself, or when it wants to feed. Insects typically inject formic acid, which can trigger a reaction, including redness, swelling, pain or itching.

Fire ants, bees, wasps and hornets have a painful sting which can trigger a potentially dangerous allergic reaction (anaphylaxis) for some people. A wasp may either bite or sting. Bites from fleas, mites and mosquitoes tend to cause itching rather than pain.

The rest of this article is about insect bites, not insect stings.

In northern countries, such as the UK, much of Europe, northern USA and Canada, biting insects include:

• Bedbugs
• Fleas
• Flies (such as horseflies)
• Gnats
• Midges
• Mosquitoes
• Spiders
• Ticks

When insects bite they release a form of saliva that can cause inflammation, blisters and irritation. Insect bite signs and symptoms vary, depending on the type of insect and the individual's sensitivity. While one person may just have a small, itchy lump that clears away in a few days, somebody else can have a more serious reaction, such as papular urticaria - crops of small papules and wheals, which may become infected or lichenified (thickened and leathery) because of rubbing and excoriation.

People who work outdoors or regularly participate in outdoor activities are more likely to be bitten by insects. In countries far away from the equator, such as many parts of Europe, northern USA and Canada, the risk of catching diseases from insect bites is small. However, the nearer the equator you get, the higher the risk is for catching diseases, such as malaria, sleeping sickness or dengue fever.

What are the signs and symptoms of insect bites?

A symptom is something the patient feels and reports, while a sign is something other people, such as the doctor detect. For example, pain may be a symptom while a rash may be a sign.

In most cases insect bites cause a small itchy lump to develop on the skin. Sometimes the bite itself may be visible (a tiny hole). The lump may be filled with fluid. The area around the lump is sometimes inflamed.

In the majority of cases insect bites are successfully treated at home and clear up within a few days.

Allergic reactions - some people, unfortunately, react badly to insect bites. Even so, severe allergic reactions are extremely rare. Allergic reactions to insect stings are more common. It is useful to know what the signs and symptoms of a severe allergic reaction are:

• A rash, often blotchy, that spreads to other parts of the body
• Breathing difficulties
• Chest pain
• Cramps
• Faintness or dizziness
• Nausea
• Rapid heartbeat
• Severe swelling which may be far from the bite area, such as the tongue or lips.
• Very severe itching
• Wheezing

If anybody has the above-listed reactions after an insect bite, call the emergency services (USA: 911 UK: 999)

If an insect bite becomes infected, the following signs and symptoms are possible:

• Pus inside the bite
• Pus around the bite
• Swollen glands
• An elevated body temperature (fever)
• A feeling of not being well
• Flu-like symptoms
• Bite area becomes redder, swells more, and becomes more painful

Some people may have a stronger reaction when they are bitten by the same type of insect for the second time; this is called sensitization - the individual becomes more sensitive to the insect's saliva. In such cases an itchy papule or an itchy weal may develop and persist for several days. Eventually, most people become immune and insensitive to the saliva if they are bitten enough times.

In the vast majority of cases insect bite reactions do not last more than a few hours. Occasionally, however, they can linger for a long time; even months. Patients with persistent long-term signs and symptoms may need medical follow-up treatment.

Tick bites - if mouth parts remain on the skin, signs and symptoms can persist. In most cases tick bite signs and symptoms clear up within three weeks. Ticks are commonly found where deer live and also in long grassy areas. Bites are not generally painful, but may sometimes cause a lump to develop where the bite occurred. However, ticks may cause Lyme disease, which is caused by Borrelia burgdorferi, a bacterium which ticks may carry.

Midges, mosquitoes, and gnats - bites tend to cause small, itchy lumps (papules). Blisters (bullae) or weals may develop in sensitive individuals.

In warmer parts of the world mosquito bites may cause many diseases, such as malaria, dengue fever, yellow fever, and encephalitis.

Fleas - particularly sensitive people may develop papular urticaria. Fluid-filled blisters (bullae) may also develop.

Horseflies - bites may cause the following signs and symptoms:

• Dizziness
• Eyes and lips may be itchy, with pink or red swellings
• Fatigue
• General weakness
• Hives (urticaria, a rash of weals)
• Wheezing

Horsefly bites may take a long time to heal. This is because the insect cuts into the skin when it bites.

Bedbugs - initial bedbug bites do not generally present any signs or symptoms. However, sensitized individuals (sensitivity increases after subsequent bites) may develop weals or papules.

Spiders - all types of spiders bite, and some of them can be quite dangerous to humans. The black widow is the most venomous spider in the USA. The brown recluse is another dangerous spider whose bite can be very damaging, causing tissue destruction and a great deal of pain.

• The female black widow spider's bite is more serious, but rarely deadly. When bitten the human feels a pinprick in the skin. At first there may only be slight swelling and faded red marks. However, within a few hours stiffness and extreme pain sets in. Signs and symptoms of a black widow spider bite may also include:
  • Chills
  • Elevated body temperature
  • Nausea
  • Extreme abdominal pain
    
    
• The brown recluse spider's bite produces a mild stinging. This is followed by redness in the bite area, and intense pain within about eight hours. A fluid-filled blister forms where the bite occurred. The blister then sloughs off, leaving a deep, enlarging ulcer. Patients may experience a mild fever, listlessness, nausea, and sometimes a rash. Death is rare, but may occur, especially in small children.

What are the causes of insect bites?

Pets - a common source of fleabites.

Crowded communities - crowded communities with low hygiene standards are common places for human flea infestations.

Birds' nests - if bird nests or bird boxes are too near a home there is a raised risk of household infestations of bird fleas.

Moving into a new home - fleas may survive for some time without hosts (animals or humans). Anybody who has recently moved house and has bites may have fleabites.

Old properties and furniture - old properties and furniture, especially with upholstery may be ideal environments for bedbugs.

Type of job - people who work outdoors have a higher risk of receiving tick bites. Mite dermatitis is more likely to be present among dockworkers, shopkeepers or warehouse workers.

Traveling - traveling from one country to another may raise the risk of being bitten by an insect.

Diagnosing insect bites

Generally insect bites are fairly easy to diagnose - the doctor will identify the signs and ask the patient about symptoms, as well as asking about any exposure to specific insects.

What are the treatment options for insect bites?

In the majority of cases insect bites reactions are mild, local and easy to treat. Patients with severe reactions should contact their doctor.

Mild local reactions - the patient will likely have some itching and localized swelling which goes away within a few days. The patient may find that placing a cold compress over the affected area, taking oral painkillers, such as Tylenol (paracetamol) or ibuprofen help. A steroid cream or anesthetic cream may also help soothe the discomfort. Some patients may find an antihistamine helps.

If the skin is broken do not apply cream or ointment directly onto it; make sure your follow the instructions on the packet.

The area may itch a lot, however, scratching it may break the skin, making it easier for bacteria to get in and cause an infection.

More serious local reactions - a short course of oral antihistamines or oral analgesic may help. In more severe cases of swelling the doctor may prescribe a short course of oral steroids.

Generalized urticaria - if the patient has small, itchy lumps or lesions near where the bite occurred the doctor may prescribe an oral corticosteroid, such as prednisolone, or an oral antihistamine. If symptoms get worse see a doctor as soon as possible.

Blisters - try not to burst them as the risk of infection will increase. A blister may not look nice, but it is rarely painful unless it ruptures. Protect the blistered area with a Band-Aid (sticky plaster).

Immunotherapy - if there are large skin reactions and more generalized symptoms, indicating possibly that the patient has become sensitized, the doctor may refer him/her to a specialist for immunotherapy (desensitization) - treatment for allergic reactions to insect bites and stings.

Bits from midges, mosquitoes and gnats - in most cases signs and symptoms will clear up on their own within a couple of days. A cold compress may be applied to reduce inflammation and possible pain if the patient has no allergic reaction. If there is itchiness and/or inflammation, OTC (over-the-counter, no prescription required) steroid creams and antihistamines may be purchased at a pharmacy (they are also available on prescription). If symptoms worsen or do not improve, see your doctor.

Bites from fleas, mites or bedbugs - the patient should try to find where the infestation is in their home. If the infestation comes from a pet it will need to be treated, as well as its bedding, and soft furnishings and carpets throughout the house. Cheyletiella mite infestation requires intervention by a veterinary surgeon.

Bedbug infestation will mean calling a good pest control company to come and decontaminate your home.

Tick bites - remove the tick immediately; this will lower your risk of a tick borne infection, such as Lyme disease. Hold the tick as close to the skin as possible and pull it straight up; make sure all its parts are removed. Twisting or jerking it as you pull pay break it and leave bits behind in your skin. Do not use petroleum jelly, alcohol or a lit match, they do not work. Wash your hands with soap and water after the tick has been removed. Clean the bite area with soap and water, apply ice to reduce the swelling, and apply an antiseptic.

Scratching the bite will probably make it swell more and raise the risk of infection. The majority of tick bites will heal within two to three weeks.

If you develop a rash around your armpit, thighs or groin, or have flu-like symptoms call your doctor. The doctor will probably prescribe antibiotics to prevent Lyme disease.

What are the possible complications of insect bites?

Secondary bacterial infection - if the bite area is scratched and the skin is broken there is a risk of a secondary bacterial infection, such as cellulitis, lymphangitis or impetigo. Sometimes the bacterial infection may coincide with the moment the bite occurs.

An oral antibiotic, such a flucloxacillin may be prescribed for staphylococcal and streptococcal skin infections, or oral erythromycin or clarithromycin if the patient is allergic to penicillin.

Lyme disease - this is caused by Borrelia burgdorferi, a bacterium. It is carried by Ixodes ricinus, a type of tick. The patient develops a red rash which eventually spreads outwards. Antibiotics generally treat the infection successfully. Untreated Lyme disease may eventually lead to meningitis, facial palsy, radiculopathy, and even in some rare cases encephalitis. There is also a risk of joint damage which can eventually result in arthritis. In some cases the patient with untreated Lyme disease may develop heart problems.

Infected ticks can also cause other diseases, such as Rocky Mountain spotted fever.

West Nile virus - this is passed on to humans by Culex spp, a type of mosquito.

Malaria - this is passed on to humans by the Anopheles mosquito. Malaria causes an infection of the red blood cells.

Preventing insect bites

When the weather is warm we tend to spend more time outdoors, exposing us to insect bites. The following steps may help reduce exposure:

• Use structural barriers, such as window screens or netting.
  
  
• If possible, avoid wooded, brushy and grassy areas.
  
  
• Avoid wearing heavily scented soaps and perfumes.
  
  
• Don't leave drinks and garbage cans (dustbins) uncovered.
  
  
• Don't wear bright colors (some insects are attracted to them).
  
  
• Whenever possible, wear long sleeves and long pants (UK: trousers).
  
  
• Tuck your pant legs into your shoes or socks.
  
  
• Wear a hat.
  
  
• Stagnant (standing) water is a breeding ground for mosquitoes. Check containers, including flowerpots, buckets, pet dishes for stagnant water.
  
  
• If non-chemical methods are not working, use an insect repellent.
  
  
• If you are camping, treat clothes, shoes and camping gear with permethrin. There are clothes which have been treated with permethrin.

Using an insect repellent

According to the Food and Drug Administration (FDA), USA, you can use an insect repellent and sunscreen at the same time - the sunscreen should be applied first.

Make sure the active ingredient in the insect repellent has been authorized by the competent regulatory agency in your country (EPA in the USA).

Spray the insect repellent on to clothes and skin, but not on to the face.

Do not use insect repellent on babies. If a child is less than ten years old make sure the repellent contains no more than 10% DEET. If the child is less than 3 years do not use oil of eucalyptus.

Follow the product's instructions carefully.

Avoid applying repellent to children's hands, around the eyes, or to areas where there are cuts and irritated skin.

Traveling - if you are traveling to an area where there is a risk of infection seek medical advice beforehand.

Camping - avoid pitching your tent near water, for example ponds or swamps.

Bedbugs - wash bedding often at a high temperature. Replace old pillows and mattresses.

Ticks - avoid areas which may be infested with ticks. Ask your local health department or park authority for information on tick-infested areas. If you are in a tick-infested area walk in the center of paths (avoid contact with vegetation).

Written by Christian Nordqvist


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