Insect and spider bites can cause small lacerations, swelling, skin discoloration, blisters, and other symptoms. Home treatment may relieve symptoms 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 person’s sensitivity.

Home treatments for insect bites include washing with mild soap and water, applying cold compresses, and raising the affected area.

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

  • bedbugs
  • fleas
  • flies, such as horseflies
  • fire ants
  • mosquitoes
  • ticks

Hiking, camping, and working outdoors can all increase the 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, painful lump 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 typically 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 longer. In this case, the person should consult a doctor.

Infections

An insect bite that develops infection can cause:

Insect bites can have different effects.

Tick bites

Tick bites are not always harmful. Often a person will experience a small rash for 1 to 2 daysTrusted Source.

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.

Mosquitoes and midges

Bites from mosquitoes and midges typically cause small, itchy lumps, or papules. Blisters may develop in some people.

Mosquito bites can transmit diseases, such as:

Fleas

A flea bite typically leads to small, raised lesions. People sensitive to insect bites might experience itching around the site for weeksTrusted Source. However, a severe allergic reaction to flea bites is rare.

Fleas can transmit diseases such as typhus and Yersinia pestis.

Horseflies

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.

Bedbugs

Bedbug bites cause discolored itchy welts. These typically occur in clusters of three to five bites.

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, people may have severe reactions to bedbug bites. A severe reaction can cause breathing difficulties, fever, and an irregular heartbeat.

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 United States.

Sand fly bites can be painful and itchy with discolored bumps and blisters. Some people may experience ulceration. The fly can also transmit diseasesTrusted Source, such as leishmaniasis.

Spiders are not insects, but they can and do bite. Some spider bitesTrusted Source 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 most commonTrusted Source in the southern and western United States. Bites may initially cause faint swelling and discoloration. Stiffness and extreme pain may follow within hours.

  • chills
  • fever
  • nausea
  • extreme abdominal pain

The risk of an insect bite depends on the environment.

For example, household pets, including cats and dogs, are a commonTrusted Source source of fleas. However, fleas can liveTrusted Source in carpets and bedding or on stray or wild animals.

Bedbugs may live in furniture, clothing, and upholstery. Regular cleaning may help people spot bedbugs, but they can appear in any environment, regardless of cleanliness.

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

A mild and limited reaction to insect bites typically passes within a few days. However, treatment may help reduce symptoms and speed up recovery.

Home remedies and over-the-counter (OTC) medication

Home remedies may relieve symptoms. To treat an insect bite at home, people can:

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

Taking over-the-counter antihistamines and pain relief may also help. A pharmacist may also suggest topical products, such as hydrocortisone cream.

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. People can remove a tick with tweezers using the following steps:

  • grasp it as close to the skin as possible
  • slowly and steadily pull upward
  • avoid squeezing the tick
  • dispose of the tick after removal
  • clean the area thoroughly

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 may 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 person to a specialist for desensitization or treatment for an allergic reaction.

If symptoms worsen or do not improve, seek medical attention.

While the swelling and discomfort from insect bites typically resolve on their own, sometimes bites can lead to further complications.

Carrier infections

Some ticks carry diseasesTrusted Source, such as rocky mountain spotted fever 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 casesTrusted Source, 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 also transmit diseases such as malaria, Lyme disease, and leishmaniasis.

The symptoms of insect bites will typically resolve by themselves, 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.