😟 “What is a furuncle? What are the symptoms and causes?”
😰 “What should I do if I develop a furuncle?”

If you are troubled by a skin lump on your face, you may have these questions.

A furuncle is a type of bacterial skin infection, also commonly known as a “boil.” It may be accompanied by redness and pain, and early treatment is important as leaving it untreated may allow the inflammation to spread.

This article explains the causes, symptoms, and treatment of furuncles. The latter half also covers prevention methods and the differences from other skin conditions, so please read to the end.

🔍 What is a furuncle?

A furuncle is a skin lump accompanied by pain and redness. It is a type of bacterial infection characterized by a firm lump with a pus-filled core at its center.

A furuncle develops when folliculitis progresses, and is commonly known as a “boil.” It can occur at any age, though furuncles tend to be more common in men than in women.

📖 Related article: Why does folliculitis occur? A thorough explanation of causes, treatment, and prevention

As a furuncle progresses further, the affected area softens over several days to weeks, eventually rupturing and discharging pus. After the pus is discharged, the pain and swelling typically subside rapidly and the condition resolves.

🔄 Why do furuncles recur? Causes explained

The cause of furuncles is infection by Staphylococcus aureus, a bacterium that normally lives on the skin. When resident skin bacteria such as Staphylococcus aureus infect a small wound or hair follicle, folliculitis develops, and when folliculitis worsens, it can progress to a furuncle.

In particular, changes in living environment that disrupt the balance of resident skin bacteria or reduce immune function can make a person more susceptible to furuncles.

⚠️ Furuncles are a skin condition that may recur repeatedly unless the underlying cause is addressed. For this reason, if the condition has become chronic, it is important to review one’s lifestyle and environment in addition to receiving treatment.

📊 What happens when you develop a furuncle? Symptoms explained

A furuncle develops when folliculitis progresses. If a furuncle progresses further, it can lead to a skin condition called a “carbuncle.”

The differences in symptoms among folliculitis, furuncle, and carbuncle are as follows 👇

⚠️ If left untreated, a furuncle may spread to multiple hair follicles and symptoms may gradually worsen, so please seek medical attention from a doctor as soon as possible.

📖 Related article: What is a carbuncle? Its relationship to furuncles and folliculitis — symptoms, causes, and treatment explained in plain language

🔬 How are furuncles examined and diagnosed?

Furuncles are diagnosed by culturing bacteria from the pus discharged from the affected area.

When a furuncle is present, bacterial culture of the pus typically detects Staphylococcus aureus.

In addition, if a furuncle has progressed to a carbuncle, elevated white blood cell counts and elevated CRP levels may be observed. CRP (C-reactive protein) is a protein that increases in the blood when inflammation or tissue damage occurs.

💊 Can you drain a furuncle? Treatment methods explained

Treatment options for furuncles are as follows 👇

Symptoms of a furuncle may be relieved by draining the pus. For this reason, treatment may involve incision and drainage.

⚠️ However, attempting to drain the pus yourself risks introducing bacteria through the wound and worsening the condition, so please do not try to drain the pus on your own — seek medical attention instead.

🛡️ How can furuncles be prevented? Prevention methods explained

Preventing furuncles involves maintaining the skin’s barrier function and supporting immune health.

Specific measures to support immune health include the following 👇

• 🌙 Maintain a regular daily routine
• 😴 Get adequate sleep
• 🧘 Take time to relax regularly and avoid accumulating stress
• 🏥 Seek treatment for any existing skin inflammation

When the skin’s barrier function and immune health are maintained, the likelihood of developing an infection is reduced even if bacteria increase on the skin. For this reason, it is important to be mindful of your daily habits and support your immune health.

It is also important to consult a doctor at the first sign of any skin discomfort to help prevent the condition from becoming more serious.

❓ Frequently asked questions about furuncles

🤔 What is the difference between a furuncle and an Epidermoid Cyst (Atheroma)?

A condition with symptoms similar to a furuncle is an Epidermoid Cyst (Atheroma).

Although their symptoms may look alike, the causes are different. The causes of each are as follows 👇

In some cases, a furuncle may also develop when the accumulated contents of an epidermoid cyst become bacterially infected.

📖 Related article: What is an Epidermoid Cyst (Atheroma)? How to receive treatment with peace of mind

🤔 What is the difference between a furuncle and acne?

The differences between a furuncle and acne are as follows 👇

Both furuncles and acne are thought to be influenced by lifestyle habits. Maintaining a regular daily routine may help in the prevention of both conditions.

📖 Related article: What causes acne? Types, symptoms, proper care, and treatment methods explained

🏥 For furuncle treatment in Tokyo, please consult IC Clinic

A furuncle is an infection that can develop in anyone when bacteria infect a small wound or clogged hair follicle.

Leaving it untreated may allow the inflammation to spread, so please seek medical attention from a doctor as soon as possible.

IC Clinic aims to be a clinic where patients of all ages and backgrounds feel comfortable seeking consultation. Whatever your symptoms, we will work with you to propose a suitable treatment approach. If you have any concerns about redness or pain on your skin, please do not hesitate to consult IC Clinic.

📌 Appointments for “furuncle (boil)” treatment are available only at the Dermatology Outpatient Department of IC Clinic Shinjuku.

📖 Detailed Symptoms and Stepwise Progression of Furuncles

⏱️ Course from onset to resolution

A furuncle does not form overnight — symptoms progress in stages. Understanding each stage makes it possible to begin treatment at the right time.

🔹 Early stage (days 1–2 after onset)

At this stage, slight redness and mild tenderness appear around the hair follicle. The area feels slightly firm to the touch, and the size is typically around 2–3 mm. Impact on daily life is minimal, and many people tend to dismiss it as minor inflammation. However, appropriate care at this stage is important — keeping the area clean and avoiding irritation may help prevent the condition from worsening.

🔹 Progressive stage (days 3–5 after onset)

Redness and swelling become noticeably greater, and pain intensifies. The affected area enlarges to approximately 5–10 mm, and a yellowish-white pus head (pus plug) becomes visible at the center. At this stage, pain may be felt from clothing rubbing against the skin or from body movement, and sleep may also be affected.

🔹 Mature stage (1–2 weeks after onset)

This is when the furuncle reaches its largest size, and the diameter may reach 1–3 cm. The central pus plug becomes more defined, and surrounding redness is at its most intense. Pain can be severe, and in some cases fever and general fatigue may occur. If appropriate treatment is not received at this stage, the risk of the infection spreading deeper increases.

🔹 Drainage and recovery stage (2–3 weeks after onset)

Once pus is discharged — either through spontaneous rupture or medical intervention — pain reduces markedly and swelling subsides rapidly. Full healing typically takes several days to one week, but by this stage, disruption to daily life is greatly reduced.

📍 Characteristics and precautions by location

😷 Furuncles on the face

Furuncles on the face — particularly around the nose and mouth — are located in an area known as the “danger triangle,” and require special caution. This area has a rich blood supply, and there is a risk of the infection spreading to the brain, so self-treatment must be avoided entirely and prompt medical attention is essential.

Characteristics of facial furuncles 👇

• 💄 Swelling is highly visible, causing significant cosmetic concern
• 🩸 Rich blood supply means the condition can progress rapidly
• ⚠️ Risk of serious complications
• 🧴 Easy to irritate during face washing or applying makeup

👔 Furuncles on the neck, shoulders, and back

These areas experience frequent friction from clothing, making furuncles prone to becoming chronic. Areas where shirt collars or bra straps press against the skin are particularly at risk.

Characteristics of furuncles on the neck, shoulders, and back 👇

• 👕 Ongoing irritation from clothing
• 👀 Hard-to-see locations mean detection is often delayed
• 🔄 Multiple sites may be affected simultaneously
• 🎨 Post-inflammatory hyperpigmentation is common after healing

🪑 Furuncles on the buttocks and thighs

Pressure when sitting and friction during walking make these areas prone to delayed healing. These locations also tend to be humid, creating an environment favorable for bacterial growth.

Characteristics of furuncles on the buttocks and thighs 👇

• 💺 Pain when sitting can be significant
• 💧 Moisture tends to accumulate, slowing healing
• 🩲 Friction from underwear can aggravate the condition
• ⚠️ Multiple furuncles in this area can progress to a carbuncle

💪 Furuncles in the axilla (underarm)

Use of antiperspirants and frequent shaving make this area one where hair follicles are easily damaged. With numerous sweat glands and a tendency to retain moisture, this is also an environment prone to furuncle development.

Characteristics of axillary furuncles 👇

• 🧴 Antiperspirants can clog pores
• 🪒 Infection can enter through microscopic nicks from shaving
• 💦 Perspiration creates a moist environment
• 🤸 Continuous irritation from arm movement

⚠️ Complications and risks of furuncles

🔥 Cellulitis

If the bacterial infection of a furuncle spreads to the subcutaneous tissue, cellulitis may develop. Cellulitis is a bacterial infection of the deeper layers of the skin and subcutaneous tissue, causing widespread redness, swelling, and warmth. High fever and chills may also occur, and intravenous antibiotic treatment may be required.

🚨 Sepsis

Although extremely rare, if the bacteria from a furuncle enter the bloodstream, they can cause sepsis, a serious systemic infection. Symptoms include high fever, rapid heart rate, and low blood pressure, requiring emergency treatment.

📸 Scar formation

If a furuncle extends deep into the tissue or is handled inappropriately, scarring may remain after healing. This is particularly a concern on the face from a cosmetic standpoint, making early and appropriate treatment important.

🔄 Chronic recurrence

If only surface-level treatment is given without addressing the underlying cause, furuncles may become chronic and recur repeatedly in the same location.

💊 Details of treatment medications and their use

💉 Oral antibiotics

The main oral antibiotics used to treat furuncles include the following 👇

🔹 Cephalosporin antibiotics

• 💊 Cefalexin (Keflex): Used as a first-line option for mild to moderate furuncles
• 💊 Cefdinir (Cefzon): Effective due to its broad spectrum of activity

🔹 Penicillin antibiotics

• 💊 Amoxicillin (Sawacillin): A standard option when there is no known allergy
• 💊 Ampicillin: Effective against susceptible strains

🔹 Other antibiotics

• 💊 Clindamycin (Dalacin): Also active against methicillin-resistant Staphylococcus aureus (MRSA)
• 💊 Levofloxacin (Cravit): Used in severe cases or when other antibiotics are ineffective

🧴 Topical antibiotics

When used in combination with oral medication, these enhance antibacterial action at the local site 👇

• 🧴 Sodium fusidate (Fucidin Leo ointment)
• 🧴 Nadifloxacin (Acuatim ointment)
• 🧴 Ozenoxacin (Zebiax ointment)

💊 Anti-inflammatory analgesics

These may be prescribed to help manage pain and inflammation 👇

• 💊 Loxoprofen (Loxonin)
• 💊 Ibuprofen (Brufen)
• 💊 Diclofenac (Voltaren)

🔪 Incision and drainage procedure for furuncles

📋 Indications for the procedure

Incision and drainage may be considered in the following situations 👇

• 💧 When pus accumulation is evident
• 💊 When antibiotics alone are insufficient to achieve improvement
• 😣 When pain is severe and interferes with daily life
• ⚠️ When spread of the infection is a concern

🔄 Procedure steps

1. 💉 Local anesthesia: A local anesthetic is injected at the treatment site to reduce pain
2. 🔪 Incision: Once adequate anesthesia is confirmed, a small incision is made in the area where pus has collected
3. 💧 Drainage: The accumulated pus is fully evacuated and infected tissue is removed
4. 🚿 Irrigation: The wound is thoroughly rinsed with saline solution
5. 🩹 Drainage placement: A drain may be placed if needed to facilitate ongoing drainage
6. 🎀 Dressing: The wound is protected with clean gauze

🏠 Post-procedure care

• 🚿 Clean the wound 1–2 times per day
• 🧴 Apply the prescribed antibiotic ointment
• 🎀 Change the gauze dressing as directed by your doctor
• ✨ Keep the wound clean and dry
• 🏃 Avoid strenuous exercise and bathing

🩺 Factors that make furuncles difficult to treat, and how to address them

🏥 Effect of underlying medical conditions

The following underlying conditions may make furuncles more difficult to treat 👇

🔹 Diabetes

High blood glucose levels impair white blood cell function, reducing the body’s ability to fight bacterial infections. Poor circulation also slows wound healing. For those with diabetes, maintaining good blood glucose control is important for both preventing and treating furuncles.

🔹 Immunodeficiency

When immune function is reduced due to primary immunodeficiency, acquired immunodeficiency syndrome (AIDS), or the use of immunosuppressive medications, furuncles are more likely to become severe and may require prolonged treatment.

🔹 Chronic renal failure

Declining kidney function leads to the accumulation of waste products in the body, reducing resistance to infection. Patients undergoing dialysis also face an increased risk of infection at vascular access sites.

🔹 Malignant tumors

When immune function is reduced by cancer treatments such as chemotherapy or radiation therapy, susceptibility to infection increases and healing tends to be slower.

🌟 Lifestyle improvement points

🔹 Improving nutritional status

• 🍖 Adequate protein intake: Consciously consume protein, which serves as the raw material for wound healing
• 🍊 Vitamin C: Essential for collagen synthesis and important for maintaining immune function
• 🥜 Zinc: An important mineral involved in wound healing and immune function
• 🥕 Vitamin A: Necessary for maintaining normal skin function

🔹 Improving sleep quality

• 😴 7–8 hours of quality sleep per night
• ⏰ Establish a consistent sleep schedule
• 🌙 Optimize the bedroom environment (appropriate temperature, darkness, and quiet)
• 📱 Limit smartphone and computer use before bedtime

🔹 Stress management

Chronic stress impairs immune function and may increase the risk of developing furuncles 👇

• 🏃 Regular exercise habits
• 🧘 Practice relaxation techniques
• 🎨 Make time for hobbies and leisure activities
• 💬 Consult a professional if needed

🍽️ The influence of diet and nutrition on furuncles

💪 Nutrients that support immune function

🔹 Vitamins

• 🥕 Vitamin A (β-carotene): Necessary for normal skin metabolism (dark green and yellow vegetables, liver)
• 🍊 Vitamin C: Important for collagen synthesis and immune function (citrus fruits, broccoli)
• ☀️ Vitamin D: Immune-regulating function (fish, mushrooms)
• 🥜 Vitamin E: Antioxidant properties (nuts, vegetable oils)

🔹 Minerals

• 🦪 Zinc: Wound healing and immune function (oysters, meat, legumes)
• 🥩 Iron: Oxygen transport and immune cell function (liver, spinach)
• 🐟 Selenium: Antioxidant properties (fish, nuts)

🔹 Protein

An essential nutrient that serves as the building material for tissue repair and immune cells 👇

• 🍖 Animal protein (fish, meat, eggs, dairy products)
• 🫘 Plant protein (legumes, nuts)
• 📊 Daily requirement: approximately 1.0–1.2 g per kg of body weight

🚫 Foods and nutrients to avoid

🔹 Excessive carbohydrate intake

• ⚠️ High blood glucose levels impair white blood cell function
• 📉 Establish eating patterns that avoid rapid spikes in blood sugar
• 🌾 Choose complex carbohydrates over refined sugars

🔹 Excessive alcohol consumption

• 🍺 Impairs immune function
• 😴 Reduces sleep quality
• 💊 Interferes with nutrient absorption

🔹 Excessive intake of high-fat foods

• 🔥 May promote inflammation
• 💧 May increase sebum production
• ⚖️ Obesity can impair immune function

🌡️ Seasonal factors and their relationship to furuncles

☀️ Precautions in summer

In hot and humid conditions, bacterial growth becomes more active, increasing the risk of furuncles 👇

🔹 Risks specific to summer

• 💦 Skin moisture from heavy perspiration
• ☀️ UV exposure weakening the skin’s barrier function
• ❄️ Sudden temperature changes from air conditioning
• 👕 Increased risk of skin injury with lighter clothing

🔹 Countermeasures

• 🧻 Wipe away sweat frequently
• 🧴 Apply appropriate sun protection
• 🌡️ Avoid sudden, drastic changes in room temperature
• 👔 Wear clean clothing

❄️ Precautions in winter

Dry air weakens the skin’s barrier function, increasing the risk of bacterial infection 👇

🔹 Risks specific to winter

• 🏜️ Reduced barrier function due to dry skin
• 🧥 Increased friction from heavier clothing
• 🔥 Sudden temperature changes from heating
• ☀️ Reduced immune function due to vitamin D deficiency

🔹 Countermeasures

• 🧴 Proactive moisturizing care
• 💧 Maintain appropriate indoor humidity (40–60%)
• 👕 Choose clothing made from natural fibers
• 💊 Consider vitamin D supplementation

👨‍👩‍👧‍👦 Preventing spread within the household

🔄 Understanding routes of transmission

Staphylococcus aureus, the bacterium that causes furuncles, can spread among family members through the following routes 👇

🔹 Direct contact transmission

• 🤝 Direct contact with the affected area
• 💧 Contact with pus or exudate
• 🌬️ Dispersal of infected skin particles

🔹 Indirect contact transmission

• 🧻 Sharing towels
• 👕 Washing clothing together
• 🛏️ Sharing bedding
• 🚿 Sharing bathroom facilities

🛡️ Measures to prevent household transmission

🔹 Basic hygiene practices

• 🧼 Thorough handwashing (with soap, for at least 20 seconds)
• 🧻 Use personal towels and toothbrushes
• 🧺 Wash clothing that has been in contact with the affected area separately
• 🧹 Clean the bathroom and toilet regularly

🔹 Precautions for the patient

• 🧼 Wash hands after touching the affected area
• 🗑️ Dispose of used gauze properly
• 🔄 Change clothing and bedding frequently
• 📏 Maintain physical distance from family members when necessary

💰 Medical costs and insurance coverage

📋 Scope of insurance coverage

Furuncle treatment is covered by health insurance 👇

🔹 Treatments covered by insurance

• 🩺 Consultation fee
• 🔬 Test fees (bacterial culture, etc.)
• 💊 Prescription medication costs
• 🔪 Incision and drainage procedure
• 🩹 Wound care

💴 Estimated treatment costs

🔹 Outpatient fees

• 🏥 Initial consultation fee: approximately ¥3,000 (30% co-payment)
• 🔄 Follow-up consultation fee: approximately ¥800 (30% co-payment)
• 💊 Prescription medication: approximately ¥1,000–¥3,000 (varies by medication)
• 🔪 Procedure fee: approximately ¥1,000–¥5,000 (varies by procedure)

🔹 Inpatient treatment for severe cases

• 🛏️ Daily inpatient cost: approximately ¥10,000–¥20,000 (30% co-payment)
• 💉 Intravenous drip cost: approximately ¥3,000–¥5,000 per day
• 🔪 Surgical cost: approximately ¥10,000–¥30,000 (varies by procedure)

📝 Summary: Living well with furuncles

Furuncles are a common skin infection that can affect anyone, yet by acquiring the right knowledge and approach, it is possible to reduce symptoms and help prevent recurrence. The key is to put the following points into practice in a comprehensive way 👇

🔹 Early detection and early treatment

• 👀 Watch carefully for changes in your skin
• 🏥 Seek medical attention promptly when symptoms appear
• 🚫 Avoid self-diagnosis and unverified home remedies

🔹 Comprehensive prevention

• ✨ Routine skin care
• 💪 Maintaining and supporting immune function
• 🏠 Addressing environmental factors
• 🌟 Optimizing your lifestyle

🔹 Ongoing self-management

• 📚 Acquiring accurate knowledge
• 🤝 Building a good relationship with your healthcare providers
• 👨‍👩‍👧‍👦 Understanding and cooperation from family and those around you
• ⏳ Taking a long-term approach to your health

If you are troubled by furuncles, we recommend not facing it alone, but seeking professional examination and treatment at a medical institution. With appropriate treatment, improvement and prevention of recurrence are achievable in many cases. In addition, improving lifestyle habits and putting prevention measures into practice can substantially reduce the risk of furuncles developing.

💬 There is no need to feel embarrassed about skin concerns. If you notice any worrying symptoms, please do not hesitate to consult a medical professional.

🌟 Seeking care early is the first step toward a faster recovery 🌟