Most people are familiar with common skin infections, a scraped knee that becomes a little red, or a pimple that becomes inflamed. However, sometimes a seemingly minor skin sore can progress into something more serious. One such condition is ecthyma, a bacterial skin infection that goes deeper than its more common cousin, impetigo. While impetigo is a superficial infection of the top layer of skin, ecthyma creates a deeper, “punched-out” ulcer that extends into the second layer of the skin. Although it is highly treatable with proper medical care, ecthyma requires a more aggressive approach than a simple surface infection to prevent complications and minimize the risk of permanent scarring.

Ecthyma is an ulcerative bacterial infection of the skin. The term “ulcerative” is key, as it means the infection creates an open sore, or ulcer, that penetrates through the epidermis (the outermost layer of skin) and deep into the dermis (the thicker layer beneath). It is often referred to as “deep impetigo” because it frequently begins as a simple impetigo lesion that, instead of healing, worsens and invades deeper into the skin tissues.

To understand the difference, it’s helpful to use an analogy. Think of your skin as a lush green lawn with a layer of rich soil underneath.

• Impetigo is like a patch of fungus that grows just on the grass surface. It is unsightly and contagious, but it is shallow and can be treated with a surface application.
• Ecthyma is what happens when that fungal patch is not treated or has an opportunity to become more aggressive. Its roots dig down through the grass layer and deep into the soil below, creating a crater-like ulcer. To fix the problem, you must not only treat the surface but also address the deeper infection within the soil itself.

This deeper invasion is why ecthyma is considered a more significant infection than impetigo and why it almost always heals with a scar.

Ecthyma is caused by bacteria infecting the skin. The specific bacteria responsible are very common and are often found living harmlessly on the surface of our skin or in our noses. They only cause disease when they are given an opportunity to breach the skin’s protective barrier and multiply within the deeper tissues.

The primary bacteria responsible for ecthyma are:

• Streptococcus pyogenes (Group A Streptococcus): This is the classic and most frequently identified cause of ecthyma. It is the same bacterium responsible for strep throat and impetigo.
• Staphylococcus aureus: This bacterium is also a very common cause and can sometimes co-infect a lesion along with Streptococcus. In some cases, methicillin-resistant Staphylococcus aureus (MRSA) may be the culprit, which requires specific antibiotic treatment.

These bacteria cause infection by releasing toxins and enzymes that break down skin tissue, allowing the infection to penetrate deeper and create the characteristic ulcer.

You get ecthyma when bacteria enter broken or irritated skin, causing a deeper infection. While anyone can develop ecthyma, certain conditions create the perfect storm for a superficial infection to progress into this deeper ulcerative form.

The most significant risk factors include:

• Pre-existing Skin Trauma: The infection almost always starts at a site of minor skin injury. Common preceding events include:
  • Insect bites, especially if they have been scratched open.
  • Cuts, scrapes, and abrasions.
  • Dermatitis (eczema), which causes breaks in the skin from dryness and scratching.
  • Scabies infestations, where intense scratching creates multiple openings for bacteria.
  • Sores from other infections, like chickenpox.
• Poor Hygiene: Not keeping wounds clean allows bacteria to multiply unchecked.
• Environmental Factors: Ecthyma is more common in hot and humid climates. Warmth and moisture create an ideal breeding ground for bacteria on the skin, increasing the likelihood and severity of infections.
• A Weakened Immune System: Individuals whose immune systems are compromised are less able to fight off the initial infection, allowing it to invade more deeply. This includes people with:
  • Uncontrolled diabetes mellitus.
  • HIV/AIDS.
  • Malnutrition.
  • Those taking immunosuppressive drugs, like chemotherapy drugs or steroids for autoimmune diseases.
• Poor Circulation: Conditions that impair blood flow to the extremities, such as peripheral vascular disease, can make it harder for the skin to heal and fight off infection.
• Crowded Living Conditions: Close contact with others can facilitate the spread of the bacteria that cause skin infections.

Patients often ask if ecthyma is a result of poor health, while it can happen in healthy people, it’s much more likely to appear when hygiene is compromised or skin is damaged.

Ecthyma typically begins as a small red bump or blister, which then ruptures and becomes a painful, deep ulcer with a thick, crusted surface.

The typical progression of an ecthyma lesion is as follows:

1. Initial Pustule or Blister: The infection usually begins as a small blister (vesicle) or a pus-filled bump (pustule) on an inflamed, reddened area of skin. This initial stage is much like impetigo.
2. Formation of a Hard Crust: The blister soon erodes, and the area becomes covered with a thick, hard crust that is typically grayish-yellow in color. This crust is often much harder and more adherent than the honey-colored crusts of impetigo.
3. The “Punched-Out” Ulcer: When the crust is removed or falls off, it reveals the hallmark sign of ecthyma: a well-defined, “punched-out” ulcer. The base of the ulcer may be filled with pus or covered in granular tissue. The edges of the ulcer are typically raised, hardened, and may have a purplish or violaceous hue.
4. Healing and Scarring: The ulcers heal slowly over several weeks. Because the infection damages the skin’s deeper dermal layer, they almost invariably heal with a permanent, sometimes discolored, scar.

Ecthyma lesions are most commonly found on the lower extremities, including the thighs, shins, ankles, and feet, but they can occur anywhere on the body. The lesions can be painful or tender, and the lymph nodes draining the affected area often become swollen and sore.

When to See a Doctor:

You should see a healthcare provider if a sore:

• Develops a thick, hard crust
• Appears deep or “punched-out”
• Is surrounded by spreading redness or is very painful
• Is accompanied by a fever
• Is not improving after a few days of basic first aid

Prompt diagnosis and treatment are the keys to a quick recovery and minimizing the risk of complications and scarring.

Diagnosis

Diagnosis is usually made by clinical examination, but in uncertain or recurrent cases, additional testing may be helpful.

• A doctor will perform a physical examination of the lesion and ask questions about how it started, any preceding injuries or insect bites, and your overall medical history.
• In some cases, the doctor may take a bacterial culture. This involves taking a swab of the pus or tissue from the base of the ulcer and sending it to a laboratory. The lab can identify the specific bacterium causing the infection and perform sensitivity testing to determine which antibiotics will be most effective. This is particularly important if methicillin-resistant Staphylococcus aureus (MRSA) is suspected or if the infection is not responding to initial treatment.
• A skin biopsy is rarely needed but may be performed if the ulcer has an unusual appearance and the diagnosis is uncertain.

Treatment focuses on eliminating the bacterial infection and supporting skin healing.

1. Wound Care and Hygiene: This is a critical component of treatment.

• Removing Crusts: The hard crusts overlying the ulcer must be removed to allow topical medications to reach the infection. This is typically done by soaking the area in warm water for 10-15 minutes or applying a warm, wet compress to soften the crust, after which it can be gently wiped away.
• Cleansing: The ulcer should be gently washed daily with an antiseptic cleanser or soap and water.
• Dressing: After cleaning, the area should be patted dry and covered with a clean, dry dressing to protect it and prevent the spread of bacteria.

2. Antibiotic Therapy: Because ecthyma is a deep infection, topical antibiotics alone are usually not sufficient.

• Topical Antibiotics: A prescription-strength antibiotic ointment, such as mupirocin, is often applied directly to the base of the ulcer after the crust has been removed.
• Oral (Systemic) Antibiotics: This is the mainstay of treatment for ecthyma. The doctor will prescribe a course of oral antibiotics, typically for 7 to 10 days. Choosing an antibiotic like cephalexin or dicloxacillin will target Streptococcus and Staphylococcus bacteria. It is essential to take the full course of antibiotics as prescribed to ensure the infection is completely cleared.

Prevention

Preventing ecthyma revolves around good skin hygiene and prompt care for any breaks in the skin.

• Wash your skin regularly with soap and water.
• Treat any cuts, scrapes, abrasions, or insect bites immediately. Clean the wound thoroughly with soap and water, apply an over-the-counter antiseptic or antibiotic ointment, and keep it covered with a clean bandage.
• Avoid scratching insect bites or other skin irritations, as this creates an entry point for bacteria.
• If you have an underlying skin condition like eczema or scabies, work with your doctor to keep it well managed to maintain a healthy skin barrier.
• For individuals with conditions like diabetes, maintaining good blood sugar control is crucial for supporting the immune system and promoting wound healing.

Ecthyma is not just a simple skin sore. It is a deep bacterial infection that creates an ulcer and requires proper medical attention. It often begins from a seemingly insignificant insect bite or scratch but can progress, especially in the presence of poor hygiene, a warm climate, or a weakened immune system. While the condition can be painful and almost always leaves a scar, the good news is that it is highly treatable. A combination of diligent wound care to keep the ulcers clean and a full course of oral antibiotics is typically sufficient to clear the infection and allow the skin to heal.

• American Academy of Dermatology Association (AADA). (n.d.). Impetigo: Diagnosis and treatment. Retrieved from https://www.aad.org/public/diseases/a-z/impetigo-treatment (Note: Ecthyma is often discussed as a form of impetigo).
• DermNet NZ. (n.d.). Ecthyma. Retrieved from https://dermnetnz.org/topics/ecthyma
• Mayo Clinic. (2022). Impetigo. Retrieved from https://www.mayoclinic.org/diseases-conditions/impetigo/symptoms-causes/syc-20352352
• World Health Organization (WHO). (2023). Infectious skin diseases. https://www.who.int