Types of Nail Fungus: Differences, Symptoms, and What You Should Know
- Published by: Payam Sarraf
- on
- | Updated on October 1, 2026
Nail fungus can appear in different forms, and each type affects the nail in its own way. The most common types include distal subungual onychomycosis, white superficial onychomycosis, proximal subungual onychomycosis, and total dystrophic onychomycosis.
In this guide, Foot + Ankle Specialty Centers explains the different types of nail fungus, how they affect the nails, and the treatment options that may help manage each condition.
5 Different Types of Fungal Nail Infections
Fungal nail infections do not all look the same. They are classified by how and where the fungus affects the nail. The main clinical patterns of onychomycosis include distal subungual, white superficial, proximal subungual, endonyx, and total dystrophic onychomycosis.
Here, we explain different fungal nail infection types, how they affect the nail, and who is more likely to develop each type. This information is based on guidance from the American Academy of Dermatology (AAD) and findings from a medical review published in the Journal of Fungi on the classification and causes of onychomycosis.
Distal Subungual Onychomycosis (DSO)
Distal subungual onychomycosis is the most common type of fungal nail infection. It starts at the tip of the nail and spreads underneath the nail plate toward the base. It may cause yellow, white, or brown discoloration, nail thickening, brittleness, and sometimes separation of the nail from the nail bed.
Who is more likely to develop it:
- Older adults
- People with diabetes or circulation problems
- People with sweaty feet or frequent moisture exposure
- People who often walk barefoot in shared wet areas, such as pools or locker rooms
DSO usually affects toenails and is most commonly caused by dermatophytes, especially Trichophyton rubrum. Its gradual spread from the nail tip helps distinguish it from other types.
White Superficial Onychomycosis (WSO)
White superficial onychomycosis affects the surface of the nail rather than starting underneath it. It usually appears as white, chalky patches on the nail that can spread and make the nail surface rough or powdery.
Who is more likely to develop it:
- People who live in warm and humid environments
- People with frequent exposure to moisture
- People with common nail fungus risk factors, such as older adults or those with diabetes
WSO is more common on toenails and is often linked to dermatophytes such as Trichophyton interdigitale. The white patches on the nail surface are the main feature that separates it from other forms.
Proximal Subungual Onychomycosis (PSO)
Proximal subungual onychomycosis begins near the cuticle, where new nail growth starts, and spreads toward the tip of the nail. It may cause white or yellow changes near the base of the nail and can lead to nail thickening or damage as it progresses.
Who is more likely to develop it:
- People with weakened immune systems
- People living with HIV or other immune-related conditions
- People with health conditions that reduce the body’s ability to fight infections
PSO is less common than DSO and is often associated with immune system problems. Its starting point near the cuticle helps distinguish it from other types of nail fungus.
Endonyx Onychomycosis
Endonyx onychomycosis affects the inner layers of the nail plate without mainly involving the nail bed. The nail may develop white or milky discoloration, but it usually does not become severely thickened or separate from the nail bed.
Who is more likely to develop it:
- People who develop dermatophyte nail infections
- People with common nail fungus risk factors, such as frequent moisture exposure or warm environments
Unlike DSO, this type mainly changes the inside structure of the nail plate while keeping the nail surface relatively intact. It is less common than other clinical forms of onychomycosis.
Endonyx onychomycosis affects the inner layers of the nail plate without mainly involving the nail bed. The nail may develop white or milky discoloration, but it usually does not become severely thickened or separate from the nail bed.
Who is more likely to develop it:
- People who develop dermatophyte nail infections
- People with common nail fungus risk factors, such as frequent moisture exposure or warm environments
Unlike DSO, this type mainly changes the inside structure of the nail plate while keeping the nail surface relatively intact. It is less common than other clinical forms of onychomycosis.
Total Dystrophic Onychomycosis (TDO)
Total dystrophic onychomycosis is the most advanced form of fungal nail infection. It can affect the entire nail and often develops after a long-lasting infection. The nail may become very thick, discolored, brittle, and distorted.
Who is more likely to develop it:
- People with long-term untreated fungal nail infections
- Older adults
- People with diabetes or weakened immune systems
TDO can develop from other types of onychomycosis when the infection continues over time. It may be caused by dermatophytes, yeasts, or non-dermatophyte molds.
What is the Most Common Type of Fungal Nail Infection?
According to the review “Onychomycosis: An Updated Review” published in the Journal of Fungi, Distal Subungual Onychomycosis (DSO) is the most common clinical pattern of fungal nail infection. It starts at the tip of the nail and spreads underneath the nail plate toward the base over time. This type may cause nail discoloration, thickening, brittleness, and separation from the nail bed.
According to the American Academy of Dermatology (AAD) overview of nail fungus, fungal nail infections become more common with age and are more likely to affect people with certain risk factors, including diabetes, a weakened immune system, or frequent exposure to warm and moist environments.
The American Family Physician review on onychomycosis reports that onychomycosis affects about 10% of the general population, with higher rates among older adults.
How Do I Know What Type of Toenail Fungus I Have?
It can be difficult to identify the exact toenail fungus types just by looking at your nails. Different types can cause similar changes, and a healthcare provider may need to examine the nail or take a sample to confirm the diagnosis.
The location of the changes, the appearance of the nail, and how the infection develops can help identify the clinical pattern of onychomycosis.
Type of Toenail Fungus | How It Usually Looks | Where It Starts |
Distal Subungual Onychomycosis (DSO) | The nail may become yellow or white, thick, brittle, and may separate from the nail bed. | Starts at the tip of the nail and spreads underneath. |
White Superficial Onychomycosis (WSO) | White, chalky patches appear on the surface of the nail. | Starts on the top layer of the nail. |
Proximal Subungual Onychomycosis (PSO) | White or yellow changes appear near the base of the nail and may spread outward. | Starts near the cuticle. |
Endonyx Onychomycosis | The nail may look white or cloudy but usually stays attached without major thickening. | Affects the inner layers of the nail plate. |
Total Dystrophic Onychomycosis (TDO) | The entire nail can become thick, damaged, discolored, and misshapen. | Can involve the whole nail, often after a long-lasting infection. |
If you notice changes in your toenails, a healthcare provider can help determine the type of fungal infection and recommend the most appropriate treatment based on the condition of your nails.
Some people also try natural remedies before seeking professional care. Learn more about one popular option in our guide: Tea Tree Oil for Nail Fungus: Does It Really Work?
When Should You See a Podiatrist for Nail Fungus?
You should see a podiatrist if your nail fungus does not improve with home care, keeps coming back, or starts causing discomfort. Professional care is especially important if the nail becomes very thick, painful, changes color, spreads to other nails, or affects your ability to walk comfortably.
Since fungi can survive in warm and damp environments, keeping shared areas and personal items clean may help reduce exposure. Learn more about Lysol for Fungus and whether it can help with fungal concerns.
People with diabetes, circulation problems, or a weakened immune system should also seek medical advice early because nail infections can be harder to manage. At Foot + Ankle Specialty Centers, Dr. Sarraf helps patients diagnose and treat nail fungus with personalized care. With over 1,000 reviews, the practice proudly serves patients in Gilbert, Scottsdale, Chandler, Mesa, and Phoenix, AZ. Call us at 480-812-3668 today to get expert help for your nail health.
Final Thoughts
Nail fungus can look different from person to person. Learning about the types of nail fungus can help you understand how the infection affects your nails. If you notice changes in your toenails, such as thickening, discoloration, or damage, seeing a podiatrist can help you find the right care and prevent the problem from getting worse.
FAQ
A podiatrist or dermatologist specializes in treating nail fungus.
There are five main types: DSO, WSO, PSO, Candida infections, and Endonyx onychomycosis.
DSO causes yellow, thick nails. WSO leaves white, chalky spots. PSO shows white discoloration near the base. Candida infections cause redness and swelling. Endonyx results in discolored nails without thickening.
Fungal infections cause discolored, thick nails, while bacterial infections often cause pain, swelling, and pus.
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Payam Sarraf
Payam Sarraf, DPM, is a podiatry specialist and surgeon at Foot + Ankle Specialty Centers, with offices in Gilbert, Scottsdale, Chandler, and Phoenix, Arizona. Dr. Sarraf’s areas of expertise include ankle trauma, Achilles tendon ruptures, podopediatrics, ankle arthroscopy and reconstruction and biomechanics.
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