Insect and spider bites can cause small lacerations, swelling, skin discoloration, blisters, and other symptoms. Home treatment includes washing with mild soap and water, applying cold compresses, and raising the affected area, but some bites may need medical attention.

Insects typically inject formic acid through their bite. This can lead to blisters, inflammation, pain, itching, and irritation. The reaction depends on the type of insect and the individual’s sensitivity.

In this article, we look at the types of insects that bite, how people react, and how to manage a bite.

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In the northern United States and Canada, biting insects include:

  • bedbugs
  • fleas
  • flies, such as horseflies
  • gnats
  • midges
  • mosquitoes
  • ticks

Hiking, camping, and working outdoors can all increase a person’s risk of insect bites.

In colder climates, the risk of catching diseases from insect bites is low. However, nearer the equator, temperatures are much higher. Here, insect bites can lead to malaria, sleeping sickness, dengue fever, or the Zika virus.

Insect bites typically cause a small itchy lump to develop on the skin. Sometimes, the bite itself may be visible as a tiny hole. The lump may fill with fluid. Inflammation sometimes occurs around the area around the lump.

Insect bites normally disappear within a few days without any need for medical attention.

Allergic reactions

Some people have an allergic reaction to insect bites. However, bites rarely cause a severe allergic reaction, unlike insect stings.

The following may indicate a severe allergic reaction:

These symptoms require immediate medical attention.

Allergic reactions to insect bites do not normally last more than a few weeks, but sometimes they can linger for months. In this case, the individual should consult a doctor.

Learn more about severe allergic reactions.


An insect bite that develops infection can lead to:

Learn more about fly bites, and find pictures of different bites here.

Insect bites can have different effects.

Tick bites

Tick bites are not always harmful. Often a person will experience a small rash for 1-2 days.

However, ticks can transmit several diseases including:

These diseases can cause muscle aches, fever, and joint pain. Without treatment, Lyme disease can cause facial paralysis, nerve damage and arthritis.

Learn more about tick bites here.

Mosquitoes and midges

Bites typically cause small, itchy lumps, or papules. Blisters or weals may develop in sensitive individuals.

Mosquito bites can transfer diseases, such as malaria, Zika, dengue fever, yellow fever, and encephalitis.

Learn more about mosquito bites here.


A flea bite typically leads to small, raised lesions within minutes. People sensitive to insect bites might experience itching around the site for a week or more.

Fleas can transmit diseases such as typhus and Yersinia pestis (Y. pestis).

Learn more about flea bites here.


Horseflies can deliver a painful bite. The following symptoms might accompany a horsefly bite:

  • dizziness
  • possible itchiness of the eyes and lips
  • fatigue
  • general weakness

Horsefly bites may take a long time to heal because the insect cuts into the skin when it bites. This can increase the risk of infection.

Learn more about horsefly bites here.


Bedbug bites cause discolored itchy welts. These typically occur in clusters.

People may not experience a reaction to bedbug bites initially, and it can take up to 14 days for symptoms to appear.

In rare cases, a person may have a severe reaction to bedbug bites. A severe reaction can cause breathing difficulties, fever, and an irregular heartbeat.

Find out more about bedbugs.

Sand flies

Sand flies are small flies that occur mostly in tropical and subtropical areas. However, they can occur in the southern states of the U.S.

The bite of the sandfly can be painful and itchy. Discolored bumps and blisters may develop. Sometimes, ulceration might result. The fly can also transmit diseases, such as leishmaniasis and the Heartland virus.

Spiders are not insects, but they can and do bite. Some spider bites are dangerous to humans.

The bite of the brown recluse, for example, produces only a mild sting at the time of the bite. However, it can be very damaging, causing tissue destruction and severe pain.

Black widow spider bites

The black widow is another venomous spider common in the United States. Bites may initially cause faint swelling and discoloration. Stiffness and extreme pain may follow within hours.

Black widow bites may cause:

  • chills
  • fever
  • nausea
  • extreme abdominal pain

Learn everything you need to know about spider bites, including symptoms and pictures here.

The risk of receiving an insect bite depends on the environment.

Common sources of fleabites include pets, crowded communities with low hygiene standards, and birds’ nests. Moving into a new home that has been empty for a while can activate dormant fleas.

Bedbugs favor old properties and upholstery. They commonly occur in low-income rental properties and hotels. They live in mattresses, clothing, and so on.

Traveling and camping can also increase the risk of insect bites.

A mild and limited reaction normally passes within a few days. However, treatment can help reduce symptoms and speed up recovery.

Home remedies and OTC medication

Home remedies can soothe discomfort and reduce swelling. To treat an insect bite at home, a person can:

  • wash the area thoroughly with soap and water
  • apply a hot or cold compress to reduce swelling
  • avoid scratching the area

Taking over-the-counter antihistamines can help to lessen the swelling from allergic reactions. Applying soothing ointments and topical antiseptics can help to reduce inflammation and prevent infection.

Tick bites

Unlike other insect bites, ticks can embed themselves in a person’s skin. Remove the tick immediately to reduce the risk of an infection, such as Lyme disease.

If a rash develops around the armpit, thighs, or groin, or an individual experiences flu-like symptoms after a tick bite, seek medical attention. The doctor will probably prescribe antibiotics to prevent Lyme disease.

Prescription treatments

A more serious local allergic reaction may require prescription antihistamines or painkillers. In more severe cases of swelling, the doctor may prescribe oral steroids.

If severe reactions in the skin and more generalized symptoms occur, the doctor may refer the individual to a specialist for desensitization or treatment for an allergic reaction.

If symptoms get worse or do not improve, seek medical attention.

While the swelling and discomfort from insect bites typically resolve independently, these bites can lead to further complications.

Carrier infections

Some ticks carry diseases, such as RMSF and Lyme disease. Borrelia burgdorferi, a bacterium that some ticks carry, causes Lyme disease. The individual develops a red rash that spreads outwards.

Without treatment, Lyme disease might lead to meningitis, facial palsy, radiculopathy, and, in rare cases, encephalitis. Other risks include joint damage, leading to arthritis, and heart problems.

Different types of mosquitoes transmit different diseases, such as the West Nile virus and malaria.

Secondary infections

A secondary bacterial infection, such as cellulitis, lymphangitis, or impetigo, can result if a person scratches the bite area and breaks the skin. Antibiotics can treat these infections.

To prevent insect bites, the following steps may help:

  • using structural barriers, such as window screens or netting
  • avoiding wooded, brushy and grassy areas
  • avoiding heavily scented cosmetics and bright-colored clothing
  • covering drinks and garbage cans
  • wearing long sleeves and long pants, tucking these into shoes or socks, and wearing a hat
  • checking containers for stagnant water, as this provides a breeding ground for mosquitoes
  • using insect repellent

Many different insects can bite humans. Insect bites can cause skin discoloration and swelling and are often itchy or uncomfortable.

Some insects, such as mosquitoes and ticks, can transmit diseases such as malaria, Lyme disease, and leishmaniasis.

The symptoms of insect bites will typically resolve independently, but home remedies such as cold compresses can help reduce swelling and discomfort.

Secondary infection of insect bites is possible without treatment, and transmitted diseases can lead to severe complications.

People can reduce their risk of insect bites by covering exposed skin when in woodland or grassy areas, using insect repellants, and using screens or netting when sleeping.

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