How to know which insect has bitten you

You probably don’t think of bruises when it comes to insect bites. Red marks, welts and itching are the most common symptoms of insect bites. However, bites from insects like spiders, hornets, wasps, mosquitoes, and ticks can cause bruising.

This article explains insect bites that can leave a bruise, insect bite symptoms, treatment, and possible complications.

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What type of insect bite leaves a bruise?

Various insects can leave a bruise after biting. Sometimes this reaction comes from the injury; other times it just appears bruised as the insect bite darkens.


It is not typical for non-venomous spiders to leave a bruise after biting. However, if you are bitten by a poisonous spider, such as a black widow or brown recluse, the bite site may turn red to purple.

In addition to a bruised appearance, other symptoms of a poisonous spider bite include:

  • Itching
  • Pain
  • Sweat
  • Difficulty breathing
  • Headache
  • Nausea or vomiting
  • Fever, chills
  • Anxiety
  • Hypertension (high blood pressure)

Poisonous spider bites require immediate medical attention.

The bees

Bee stings, especially those from hornets and wasps, are painful. Although not a primary symptom of a sting, a bruise may occur around the sting due to the injury.

Other symptoms of hornet and wasp stings include:

  • Pain
  • Redness
  • Swelling
  • Itching

Allergic reactions

Signs of an allergic reaction include flushing, hives, dizziness, difficulty breathing, and loss of consciousness.


Mosquitoes are well known for their itchy red welts. But bruising can also occur, especially in people allergic to mosquitoes, known as “Skeeter syndrome”. Skeeter syndrome is usually not a life-threatening allergy.

Other symptoms include:

  • Large areas of swelling
  • Heat
  • Redness
  • Itching

Skeeter’s syndrome usually improves within a few days. If your symptoms get worse or last longer, see a doctor about a possible skin infection.


Tick ​​bites are painless, which is why it’s essential to check your body after spending time outdoors in tick-infested areas. When a tick embeds itself in your skin, the site may appear red or purple.

After the bite, a rash is common, especially with tick-borne disease. The rash can look like a target and is often pink or red, but it can also be darker in color.

Other symptoms of a tick-borne disease include:

  • Fever
  • Chills
  • Headache
  • Fatigue
  • Muscle aches

Be aware that symptoms of a tick-borne illness can take up to a few weeks to develop. If you experience any of the above symptoms after spending time outdoors, talk to a healthcare professional.

If a bruise is accompanied by symptoms of allergy or poisoning, such as difficulty breathing, wheezing, nausea, or confusion, seek medical attention immediately.

Other Symptoms of Insect Bites

Symptoms of insect bites vary; however, they often share some common traits. These include:

  • Redness
  • welts
  • Urticaria
  • Pain
  • Itching

What is anaphylaxis?

Anaphylaxis is a life-threatening allergic reaction that requires immediate medical attention. Symptoms include:

  • Itching
  • Wheezing
  • Shortness of breath
  • Confusion

Causes of bruising from insect bites

Often the cause of purple skin around an insect bite is your body’s reaction to the insect’s saliva or venom. For example, when a mosquito sucks your blood, it injects saliva into your skin. This fluid exchange produces an itchy rash in most people and can also lead to a bruised appearance.

Other times, like with a bee sting or a spider bite, when the venom is released into the skin and surrounding tissue, it causes pain and inflammation. These reactions can sometimes lead to bruising.

Some insect vectors (those responsible for spreading human disease), such as ticks, can cause a rash that appears purple. These rashes are different from other insect bite reactions because they indicate a systemic (body-wide) infection rather than a localized skin reaction.


Usually insect bites are a minor annoyance, but sometimes they can be more of a concern. Therefore, the first step in dealing with an insect bite is to identify the culprit, as this may determine the actions you take.

If you have a non-venomous, allergic, or infectious bite, the following is recommended:

Also, take preventative measures to avoid insect bites by using insect repellent containing DEET when spending time outdoors and keeping your skin covered with clothing.

Complications of insect bites

Complications from insect bites include allergic reactions, skin infections, poisoning, and necrosis (skin and tissue death).


Allergies to stings and insect stings require immediate medical attention. Signs of an allergic reaction include:

  • Rinsing
  • Urticaria
  • Swelling
  • Dizziness
  • Difficulty breathing
  • Nausea
  • Loss of consciousness
  • Shock

About 15% of deaths from anaphylaxis (severe allergic reaction) are due to venom allergies.

Skin infections

Since insect bites break the skin, they can lead to infection. Symptoms of a skin infection include:

  • Eruption
  • Swelling
  • Redness
  • Pain
  • Pus
  • Itching


Necrosis occurs when an infection causes the skin and surrounding tissue to die. This type of infection is more likely with poisonous spiders. Necrotizing infections are dangerous and require immediate medical attention. Symptoms include:

  • Swelling
  • Blisters
  • Skin that turns purple or black
  • high fever
  • rapid heartbeat
  • Confusion
  • Unconsciousness


Not all spider bites can make you sick, but some can. Symptoms of a poisonous bite include:

  • Pain
  • Swelling
  • Necrosis
  • Fever
  • Difficulty breathing

Seek immediate medical attention if you experience the above symptoms after a spider bite.


Some insect bites can cause a bruise or bruise-like appearance. Insects that can cause bruising include mosquitoes, ticks, bees, and spiders. Often a bruise is nothing to worry about, but keep an eye out for allergy symptoms, skin infections, necrosis and more after a sting or insect bite. If any of these warning symptoms accompany your insect bite bruise, seek medical attention immediately.

A word from Verywell

Most of the time, insect bites are only a minor annoyance. However, sometimes they can be more concerning. If you’ve been bitten or stung, keep an eye out for concerning symptoms. If you’re not sure if you should be concerned, it’s best to err on the side of caution and see a doctor.

Frequently Asked Questions

  • Is it dangerous if an insect bite turns purple?

    It’s not necessarily dangerous if an insect bite turns purple. Sometimes insect bites can cause bruising from the injury. However, in some cases, it can be concerning, as it can be a sign of necrosis (death of skin and tissue). If purple skin is accompanied by symptoms of infection or allergy, see a doctor.

  • How to recognize a spider bite?

    Identifying the type of insect that bit you is not always easy. However, some things can offer clues. For example, if you were bitten on the inside and the bite is painful, it may be a spider. If the spider was venomous, you may notice other symptoms, such as swelling, necrosis, fever, or difficulty breathing.

  • Can mosquitoes bite through clothing?

    Yes, mosquitoes can bite through clothing. Although covering exposed skin is a good precaution, using insect repellent is also a good idea.