Skin Sores and Lesions: Causes and Treatments

Medically Reviewed By Meredith Goodwin, MD, FAAFP

A sore can be a blister, bump, lesion, wound, or ulcer. Common causes include injuries and skin infections. More serious causes include certain viral infections, diabetes, and skin cancer. A sore may be painful, itchy, discolored, swollen, or tender to the touch. It may be hard or filled with fluid. The sore may bleed and ooze other fluids. Depending on the cause, you may have only one sore or many at a time.

Sores are not typically medical emergencies. However, you should seek medical help if your sore seems infected, painful, or does not improve. If you have numerous sores, a clinician can help treat them.

This article explains the features and causes of sores, how to treat different types of sores, and when to contact a doctor.

What can cause sores

large bandage on lower leg
DragonFly Production/Stocksy United

Sores can occur due to injuries and a variety of different conditions. Some sores may require a medical diagnosis and treatment. Below is a summary of sores and possible causes.

Injuries, sores, and healing

Injuries that break the skin can cause a sore, and your body immediately jumps into action to heal it. This occurs in 4 stages:

  1. Blood clotting and scab formation: If there is bleeding, platelets and other clotting factors in the blood work to stop it. These factors form a scab, which protects the underlying skin from dirt and germs. It only takes a few minutes for blood to clot.
  2. Inflammation: Your immune system sends different cells and substances to stimulate healing and protect the sore from infection. The injured area may become tender, flushed, and swollen. It may also ooze clear fluid. This stage takes a few days but may take longer for larger sores.
  3. Rebuilding: The cells in the area form new cells to replace those lost. Blood cells bring oxygen and other nutrients to the area. Strong connective tissues form to provide structure to the area.
  4. Strengthening: New cell and connective tissue growth continue to strengthen the area.

Burns are a common injury that may lead to a blister. Do not burst a blister. It is your body’s response to the burn and protects the underlying skin from infection. Let the blister heal itself naturally.

Learn more about the symptoms of an infected cut and how to treat burns.

Canker sore

A canker sore is an ulcer inside your mouth. They are usually white or yellow with a red or brown rim and can be very painful. Most canker sores heal on their own without treatment. If you get canker sores frequently, contact your doctor about potential food allergies.

At-home remedies for canker sores include baking soda pastes and mouth rinses, cool compresses, and over-the-counter (OTC) numbing agents.

Sores in the mouth can also occur due to a viral infection, especially hand, foot, and mouth disease. This infection is more common Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source  in children than adults. Symptoms may include a rash on the hands and feet, and flu-like symptoms, such as fever, headache, and fatigue.


Extended bed rest or use of a wheelchair may cause bedsores. These sores develop due to limited blood flow to areas under constant pressure from the bed or chair.

The first step in bedsore treatment is to relieve the pressure. Using an egg crate-style foam mattress or pad may help. Keep the sore clean and dry, and cover it with a bandage.

Contact a medical professional about bedsores that are unusually large or not improving.

Genital and oral herpes sores

The herpes simplex virus (HSV) is a common cause of recurrent mouth, finger, or genital sores. Your clinician may refer to these as cold sores or fever blisters when they appear on the mouth.

HSV-1 mainly causes lesions on the mouth or eyes. HSV-2 is the main cause of genital herpes. Herpes lesions appear as blisters first, then turn into sores. You may feel a tingling sensation in the area before the sores appear.

The herpes lesions heal on their own, but a healthcare professional can prescribe antivirals to speed the healing process. Self-care for the sores includes cold compresses and OTC pain relievers if necessary. Clean and dry the sores daily.

Yeast sores

Sores are not common with yeast infections, but they are possible. Candidiasis, a type of yeast infection, can affect Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source  the vagina, mouth, throat, and esophagus. Vaginal yeast infections can be very itchy, leading to sores from scratching. Severe infections can lead to tears in the vaginal tissues and other infected areas, such as the corners of the mouth.

Treatment is usually an antifungal medication you apply directly to the infected area or take by mouth. A sitz bath can also help soothe a vaginal yeast infection. Gently pat the area dry and wear loose-fitting clothing.


Varicella-zoster virus causes both chickenpox and shingles. The virus causes fluid-filled blisters to cluster in a small area, usually Trusted Source National Institute on Aging Governmental authority Go to source  on one side of the torso. Contact a healthcare professional if you think you have shingles, as early treatment can help.

Treatment options include prescription antivirals, pain relievers, and corticosteroids. Cold compresses, calamine lotion, and OTC pain relievers may also help reduce symptoms. Eventually, the blisters will scab and fall off.

Other infections

Other infectious causes of sores include:

Contact allergies

Sometimes, sores are an immune response to an allergen. Another name for this response is allergic contact dermatitis. The immune system can overreact to even small amounts of a substance, causing a rash to develop. Blisters can result from Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source  a severe reaction. Common allergens include:

  • latex
  • nickel
  • plants
  • topical medications

Steroid creams can reduce swelling, irritation, and itching. If OTC creams are ineffective or you have a severe skin reaction, contact a doctor.

Insect bites and stings

Many insect bites and stings can cause sores. These include bites or stings from:

  • mosquitoes
  • biting flies
  • hornets
  • spiders

Sores can develop from scratching a bite or sting. They can also develop from an allergic reaction to the venom.

Bacteria can also enter a bug bite or sting, potentially causing infection. Contact a medical professional if your bite or sting looks infected or has significant swelling.


Sores that take a long time to heal can indicate prolonged high blood sugar from diabetes. This condition causes blood vessel and nerve damage and reduces circulation. The reduced circulation makes it hard for your body to heal sores and wounds, increasing your risk of skin ulcers.

Whether or not you have a diabetes diagnosis, contact a doctor for unexplained sores or wounds, especially those that last longer than 1 week.


A sore that does not heal Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source may also be a sign of skin cancer. Certain types of leukemia can cause skin lesions.

Learn more about leukemia cutis.

Other causes of sores

In addition to cancer, underlying conditions that can cause sores include:

When to contact a doctor for a sore

Sores that do not seem to heal require medical attention. You should contact a doctor for a sore that is:

  • large or extends beyond the top layer of skin
  • not healing
  • infected
  • warm to touch, swollen, or discolored
  • accompanying other symptoms, such as:
    • bleeding or bruising
    • tingling, burning, or other unusual sensations
    • joint pain, stiffness, or discoloration
    • red streaks moving away from the sore
    • high fever
    • reduced urine production
    • dizziness

Symptoms that might indicate a more serious condition

Sometimes sores accompany symptoms of a more serious condition. For example, an infection from a sore can spread further into the body or bloodstream and cause sepsis.

Seek immediate medical care by calling 911 for serious symptoms, such as:

Read about septic shock.

Frequently asked questions

Meredith Goodwin, M.D., has reviewed the following frequently asked questions.

Why won’t my sores heal?

Possible causes of a sore that will not heal include a low immune system, skin cancer, and limited circulation. Conditions such as peripheral artery disease or diabetes can also cause persistent sores. Contact a doctor promptly for symptoms of infection or a sore that takes a long time to heal.

Which ointment is best for wound healing?

Petroleum jelly is best for wound healing and scar prevention, according to the American Academy of Dermatology Association. After cleaning the sore, apply the ointment and cover it with an adhesive bandage. Use a hydrogel or silicone gel sheet for large sores, and change it daily.


Injuries, infections, and underlying medical conditions can cause sores. Some sores heal on their own, and others need treatment.

Contact a medical professional for sores that cover a large area, look infected, or do not heal as expected. Seek care for sores with additional symptoms, such as significant pain, fever, or general illness.

Medical Reviewer: Meredith Goodwin, MD, FAAFP
Last Review Date: 2022 Aug 11
View All Skin, Hair and Nails Articles
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.