Types of Nail Fungus: DLSO, White, Proximal, Candida
Short answer: Clinicians group nail fungus (onychomycosis) by where the infection starts and what organism causes it. The main patterns are distal and lateral subungual (the most common, starting at the nail tip or side), white superficial (chalky surface patches), proximal subungual (starting at the base, linked with weakened immunity), candidal (yeast, often fingernails), and total dystrophic (an advanced stage). Only a lab test confirms which you have.
Key takeaways
- The types differ by where the infection starts and which organism is involved, not by how bad it looks.
- Distal and lateral subungual is the most common pattern; proximal is less common and is associated with weakened immunity, so it is a reason to see a doctor.
- Yeast (candida) and molds can infect nails too, and they may need different treatment from the usual dermatophyte infection.
- Many other conditions look like nail fungus, including psoriasis, injury, bacterial stains and, rarely, melanoma. A lab test avoids guessing.
In this guide
- Nail fungus types at a glance
- Distal and lateral subungual onychomycosis (DLSO)
- White superficial onychomycosis (WSO)
- Proximal subungual onychomycosis (PSO)
- Candidal nail infections (yeast)
- Mold infections and mixed infections
- Total dystrophic onychomycosis
- Why the lab test matters
- Who tends to get which kind, and why it matters
- Why we do not show photo galleries
- Prevention applies to every type
- What each type means for treatment
- Can it be melanoma? Why dark streaks are different
- Frequently asked questions
- Sources
Nail fungus types at a glance
The word onychomycosis simply means a fungal infection of the nail. Dermatology textbooks and review articles (for example StatPearls) classify it into patterns based on how the fungus enters and where it spreads. Names vary slightly between sources, and a nail can show a mix. The table is a plain-language map, not a diagnosis.
| Type | Where it starts | What you may see | Who it is linked with |
|---|---|---|---|
| Distal and lateral subungual (DLSO) | Under the nail tip or side edge | Yellow, white or brown color change; thickening; debris under the nail; lifting | Most common pattern; toenails especially |
| White superficial (WSO) | The nail surface | Chalky white patches that can look powdery | Mostly toenails; less common than DLSO |
| Proximal subungual (PSO) | Under the base of the nail by the cuticle | White or yellow area near the cuticle moving outwards as the nail grows | Uncommon; associated with weakened immunity |
| Endonyx | Within the nail plate | Milky white nail without thickening or lifting | Less common; reported in some sources as a separate type |
| Candidal (yeast) | Nail fold or nail plate | Swollen, red nail fold; nail ridges or discoloration; often fingernails | Hands often wet; sometimes diabetes or immune problems |
| Mold infection | Nail plate | Varied; can be brown, green or black tones | Damaged nails; needs a lab test to identify |
| Total dystrophic (TDO) | The whole nail unit (advanced) | Thick, crumbly, distorted nail | End stage of other types |
The AAD describes the first sign as usually a different color on part of a nail, with brittleness, debris under a discolored nail and lifting as other signs. Toenails are affected most often, but fingernails can be too (NHS).
Distal and lateral subungual onychomycosis (DLSO)
This is the pattern most people mean by “toenail fungus”. The infection starts at the free edge or the sides of the nail, where it meets the skin, and moves toward the base. The nail often turns yellow, white or brown, thickens, and develops a chalky layer of debris underneath. The nail may lift away from the nail bed (onycholysis), which can hurt in shoes. The fungi involved are usually dermatophytes, the same group that causes athlete’s foot, which is why treating athlete’s foot matters.
Early signs are easy to miss; see early stage nail fungus symptoms for what to look for. For how colors are read, see nail fungus color: what it means.
White superficial onychomycosis (WSO)
Here the fungus sits on the surface of the nail plate rather than underneath. White, chalky or powdery patches appear on the top of the nail and may be scraped off partially. It is mostly a toenail pattern. Because it is superficial, it is described differently from DLSO in textbooks, though a clinician still needs to confirm it, since other causes of white nails exist (injury, a harmless white mark from a knock, and some skin conditions).
Proximal subungual onychomycosis (PSO)
In PSO the infection begins at the base of the nail, near the cuticle, and moves outward as the nail grows. Review articles describe it as uncommon in healthy people and associated with immune problems. That makes a proximal pattern one of the reasons to see a doctor instead of trying a home remedy: it can signal that the immune system deserves attention. Do not self-diagnose from this; many other things can cause white at the base of the nail, and a clinician can examine the nail, ask about your health history, and decide whether any further checks are sensible.
Candidal nail infections (yeast)
Yeasts of the Candida family can affect nails, usually fingernails. A common pattern is a swollen, red, tender skin fold around the nail (paronychia). The Merck Manual notes that chronic paronychia mainly occurs in people whose hands are often wet, especially those with hand eczema, diabetes or a weakened immune system, and that yeast is often present although its exact role is unclear. Treatment often centres on keeping hands dry and protected, with prescription creams or other measures, rather than the standard nail-fungus tablets. See also fingernail fungus vs toenail fungus.
Mold infections and mixed infections
Some nail infections are caused by non-dermatophyte molds, and some involve more than one organism. They can look like other types, which is one reason clinicians use laboratory tests. Treatment choices can depend on the organism, and some standard antifungals work less well against certain yeasts and molds.
Total dystrophic onychomycosis
This label describes a nail in which the whole nail unit is thick, crumbly and distorted. In most descriptions it is the advanced end point of other types rather than a separate cause. A nail this affected may be painful, may catch on socks and shoes, and may need debridement by a podiatrist. See what a podiatrist does and toenail fungus and a nail falling off.
Why the lab test matters
Looks alone cannot tell the types apart, and they can resemble other conditions. The NHS says a GP may take a sample of the nail and test it to identify the type of infection before prescribing tablets, and that you may need a blood test before and during treatment to check your liver. The AAD adds that prescription medication is needed. If you are about to spend money on any treatment, confirming what you are treating is the most useful first step.
- Nail psoriasis can cause pitting, thickening and discoloration; see nail fungus vs nail psoriasis.
- Injury and bruising under the nail; see bruised nail vs fungus.
- Yellow nails without infection; see yellow toenails without fungus.
- Bacterial stains such as green nail syndrome.
- Skin cancer under the nail, which is rare but important not to miss.
Who tends to get which kind, and why it matters
Risk factors overlap across types: older age, athlete’s foot, nail injury, warm and damp shoes, shared wet spaces such as pool decks and locker rooms, diabetes, poor circulation and a weakened immune system. The AAD says fungi spread by touching infected skin or nails, sharing items such as clippers, or walking barefoot in warm, moist places. What differs by type is mostly which organism and which part of the nail are involved, and therefore what a clinician considers first.
- A toenail pattern that starts at the tip is most often the common dermatophyte kind, and reinfection from shoes and socks is a typical reason it returns; see why it keeps coming back.
- A fingernail pattern with a swollen, tender nail fold points toward wet-hands inflammation, where yeast may or may not be the main driver.
- White at the base of a nail is a reason to mention your health history and medicines to a doctor, including any immune-affecting conditions or drugs.
- A single nail with an odd color that does not fit the patterns above deserves a closer look rather than another round of home treatment.
Why we do not show photo galleries
You may notice that guides to nail fungus types often include photo galleries. We have chosen not to use unlicensed clinical photographs here, and we do not think photos should be used to self-diagnose: the same photo can fit several conditions, lighting changes colors, and the difference between fungus, psoriasis and a bacterial stain often needs a laboratory test. If you want a visual comparison, your clinician can show you one from a licensed medical atlas.
If you already have a diagnosis, the practical next step is not to find the best matching picture but to ask what the treatment plan is, what to expect month by month, and how long you will be monitored. For realistic timelines, see how long home remedies take and will toenail fungus go away on its own?.
Prevention applies to every type
The AAD and NHS give the same basics for any type: keep nails short, clean and dry; wear clean socks; treat athlete’s foot promptly; wear flip-flops in gym and pool showers; do not share clippers, towels or shoes; and choose well-fitting shoes that do not make your feet hot and sweaty. See also how to disinfect shoes and socks and shoes for prevention, and is nail fungus contagious?.
What each type means for treatment
Treatment is chosen by a clinician and generally depends on the organism, how much of the nail is affected, which nail, your other health conditions and your other medicines. Options include prescription nail lacquers, oral antifungals (with liver monitoring for some), and procedures such as debridement. For the medicines, see our guides on terbinafine, itraconazole vs terbinafine and ciclopirox lacquer. For who to see, read podiatrist or dermatologist.
Nails grow slowly, so success is judged by the new nail growing in clear. On the big toe the AAD says it may take a year or longer to see a clear nail. No type clears overnight, and no type should be treated with an untested remedy in place of medical advice.
Can it be melanoma? Why dark streaks are different
Most dark marks under a nail are not cancer, but a new brown or black streak or band, especially one that is widening, darkening, or that extends onto the surrounding skin, needs a specialist. The AAD recommends making an appointment with a board-certified dermatologist for any nail change, including a new dark band. If you are unsure, do not wait.
See a doctor soon if
a nail is painful, swollen, oozing or lifting; the infection is spreading to other nails; you have diabetes, poor circulation, or a weakened immune system; the skin around the nail is red, hot or swollen; you have a fever; or there is a new dark streak, band or spot in the nail or darkening of the skin beside it.
Questions to ask your doctor or clinician
- Which type of nail infection do I have, and how can we confirm it with a lab test?
- Could this be something other than fungus, such as psoriasis, injury or a bacterial stain?
- Does the type change which treatment you recommend?
- Do my other conditions or medicines change my options?
- How long until we can tell whether treatment is working?
Frequently asked questions
What is the most common type of nail fungus?
Distal and lateral subungual onychomycosis (DLSO), where the infection starts at the nail tip or side and moves toward the base, is the most commonly described pattern.
Can nail fungus be white?
Yes. White nail changes can come from white superficial onychomycosis and from some other patterns, and from harmless causes such as small knocks. A lab test confirms fungus.
What is proximal onychomycosis?
It starts under the base of the nail near the cuticle. It is uncommon and is associated with weakened immunity, so a doctor should be involved.
Can yeast infect fingernails?
Yes. Candida can affect the nail fold and nail, especially when hands are often wet. A doctor can tell yeast from fungus and plan treatment.
Do all types of nail fungus need the same treatment?
No. Treatment depends on the organism, how much of the nail is affected, and your health. A nail sample helps your clinician choose.
Related reading
- Early stage nail fungus symptoms
- Nail fungus color: what it means
- Nail fungus vs nail psoriasis
- Fingernail fungus vs toenail fungus
- Podiatrist or dermatologist for nail fungus
Sources
- AAD nail fungus overview https://www.aad.org/public/diseases/a-z/nail-fungus-overview
- NHS fungal nail infection https://www.nhs.uk/conditions/fungal-nail-infection/
- AAD nail melanoma https://www.aad.org/public/diseases/skin-cancer/types/common/melanoma/nail-melanoma
- Merck Manual (consumer): chronic paronychia https://www.merckmanuals.com/home/skin-disorders/nail-disorders/chronic-paronychia
- StatPearls: Onychomycosis https://www.ncbi.nlm.nih.gov/books/NBK441853/
- Journal of Drugs in Dermatology: Onychomycosis, an overview https://jddonline.com/articles/dermatology/S1545961613S0096X
Medical disclaimer. This page is general educational information, not medical advice, and it has not been reviewed by a doctor. It cannot diagnose your nail. Always talk to your doctor, podiatrist, dermatologist or pharmacist about your situation; see our medical disclaimer. Last reviewed by our editorial team: 20 October 2026.
