You’ve noticed your fingernails have recently developed a yellow or brown color. Maybe one of your toenails seems thicker than usual. How do you know if it’s nail psoriasis, nail fungus, or both?

“My doctor just looked at my nails and treated me for fungus, but it was not a fungus,” said one MyPsoriasisTeam member. “It was the beginning of a life with psoriasis.”

Psoriasis of the nails and fungal infections of the nails (also called onychomycosis) can cause overlapping symptoms. However, there are a few clues to help you and your health care provider determine the difference. In this article, we look at five differences in causes, symptoms, and treatments.

1. Nail Psoriasis Is Not Contagious

Psoriasis is a chronic (ongoing) skin condition that often affects the knees, elbows, and scalp but can affect the nails, too. Psoriasis is an autoimmune disease. It develops when part of the immune system becomes overactive, leading to skin changes and sometimes psoriatic arthritis and nail changes. Nail psoriasis is not contagious.

Fungal infections develop when a fungus comes into contact with the skin or nails and finds favorable conditions for growth, like a warm and moist environment. Fungi (plural of fungus) can spread from person to person, animal to person, and object to person. Nail fungal infections are contagious.

Nail Psoriasis Causes

While experts do not yet fully understand what causes psoriasis, you may notice triggers that lead to flare-ups. Nail psoriasis causes and triggers include:

• Family history of psoriasis
• Stress
• Skin injuries, like cuts, scrapes, or sunburns
• Smoking or heavy alcohol consumption
• Illness, like bronchitis or tonsillitis
• Infection, like strep throat or a skin infection
• Cold, dry weather

Nail psoriasis is common in people with psoriasis and psoriatic arthritis. According to the National Psoriasis Foundation, an estimated 90 percent of people with psoriasis will develop psoriatic nails at some point in their lifetime. Nail psoriasis can also be an early indication of psoriatic arthritis, which affects approximately 30 percent of people with psoriasis.

Nail Fungus Causes

Fungal infections are caused by a fungus, like yeast or mold. The fungi most often linked to nail fungal infections are dermatophytes, which also cause ringworm and athlete’s foot. Dermatophytes can live on skin, bedding, clothing, towels, household objects, and surfaces. Fungal infections can also affect your skin, mouth, throat, lungs, and other parts of your body.

Nail fungus causes and risk factors include:

• Getting older
• Living in a hot, humid climate
• Walking barefoot on damp surfaces, like in the shower or locker room at the gym
• Having a history of athlete’s foot
• Wearing plastic gloves daily, like at work
• Sharing an infected towel or nail clipper
• Having a skin or nail injury
• Getting a manicure or pedicure at a nail salon

The American Academy of Dermatology also lists psoriasis as a risk factor for nail fungus, since psoriatic nails can split or lift from the nail bed, leaving you more susceptible to infection.

While you cannot spread nail psoriasis to other people, the same is not true of fungal nail infections. If you’ve been diagnosed with nail fungus, ask your health care provider how to protect your friends, family, and other people from getting it.

2. Nail Psoriasis Is Unlikely To Cause an Odor

Nail changes or discoloration accompanied by a foul odor are more likely to indicate nail fungus than nail psoriasis. That unpleasant smell is caused by microorganisms feeding on your body. While not all fungal nail infections smell, a foul odor is not a symptom of nail psoriasis.

Nail Psoriasis Symptoms

While plaque psoriasis often causes raised, scaly patches on the skin that may flake, itch, burn, or sting, psoriatic nail disease creates symptoms unique to the fingernails and toenails.

Symptoms of nail psoriasis include:

• Pitting — Divots or small pits on the surface of the nail
• Discoloration — Red, yellow, pink, or dark brown splotches
• Nail plate thinning — A structural change that may cause the nail to peel or crumble
• Beau’s lines — Horizontal grooves across the nails
• Subungual hyperkeratosis — Chalky buildup or lesions beneath the nail plate
• Splinter hemorrhage — Splinter-shaped blood clots under the nail
• Onycholysis — Nail plate separation from the nail bed
• Tenderness or pain around the nail

While nails lifting off the nail bed is a symptom of nail psoriasis, it can also lead to the development of nail fungus because it creates an opening for the fungus to enter and grow.

Nail Fungus Symptoms

In addition to an unpleasant smell, a fungal nail infection can create other symptoms that affect the fingernails and toes. Symptoms of nail fungus include:

• Discoloration — White, brown, or yellow patches that spread over time
• Nail plate thinning — Soft, dry, powdery nail texture
• Nail plate thickening — Misshapen nails
• Structural changes — Splitting or crumbling nails
• Onycholysis — Nail plate separation from the nail bed

Nail fungus is unlikely to cause pain.

As you can see, there is an overlap between symptoms of nail fungus and nail psoriasis. You can also experience both conditions at the same time. Furthermore, the pitting seen with nail psoriasis can be a symptom of other skin diseases, like eczema or vitiligo. White nail discoloration, or leukonychia, can indicate other health issues. Getting an accurate diagnosis is essential.

3. Nail Psoriasis Is More Common on the Fingers

Nail psoriasis and nail fungus can both affect your hands and feet, but nail psoriasis is

more likely to develop on your fingernails. Nail fungus is more likely to affect your toenails.

During a physical exam, your doctor or dermatologist may consider the location of the nail disease when diagnosing you with nail psoriasis, nail fungus, or another nail disorder. Experts do not yet know why nail psoriasis is more likely to affect the fingernails. The connection between nail fungus and toenails is easier to understand.

Why Does Toenail Fungus Happen?

Fungal infections are more likely to affect the toes because fungi thrive in warm, moist environments, like inside sweaty socks and shoes. They also prefer darkness. Unless you have a job where you regularly wear gloves for hours at a time, your hands are less likely to create a welcoming environment for fungus — except when you have a cut or crack in your fingernail that allows the fungus to enter.

If you have recurring toenail fungus, you may have athlete’s foot.

4. Nail Psoriasis Often Affects Multiple Nails

Another factor your health care provider might consider is how many fingernails or toenails are affected. Nail psoriasis tends to develop on multiple nails. Nail fungus generally affects just one nail at first, although it can spread.

Diagnosing Nail Psoriasis and Nail Fungus

Diagnosing nail disease can be difficult because symptoms overlap, and it’s possible to have more than one condition. Your doctor or dermatologist will likely start by performing a physical exam and asking about your symptoms.

If your doctor suspects a fungal nail infection, they might send samples of debris from under your nails or nail clippings to a lab for analysis. If they suspect psoriasis, they might examine the rest of your body for psoriasis symptoms because of the prevalence of psoriatic nail disease in people with other types of psoriasis.

Make an appointment with your health care provider if you notice any nail changes or possible symptoms of nail disease.

5. Nail Psoriasis Treatments Target the Immune System

Although nail psoriasis and nail fungus can look similar, they require different treatments. Nail psoriasis is an autoimmune disease. To ease your symptoms and make you more comfortable, your health care provider will likely recommend treatments to target the immune system and calm inflammation. For nail fungus, they will likely recommend topical and oral antifungal medications.

Nail Psoriasis Treatments

Your health care provider will recommend treatment options based on your diagnosis, disease severity, overall health, whether you have psoriasis elsewhere on your body, and other factors.

Treatments for nail psoriasis include:

• Topical steroids applied to the nail or nail bed
• Other topical therapies, like calcipotriene (Dovonex), cyclosporine, or vitamin D
• Corticosteroid injections under the nail
• Oral medications, like methotrexate (Trexall) or apremilast (Otezla)
• Phototherapy (light therapy)
• A retinoid called tazarotene (Tazorac), a synthetic form of vitamin A
• Laser therapy
• Janus kinase (JAK) inhibitors, like tofacitinib (Xeljanz)
• Biologics, like adalimumab (Abrilada), etanercept (Enbrel), or ustekinumab (Stelara), or ixekizumab (Taltz)
• Nail removal

Treating nail psoriasis can be difficult, and you may need to try multiple treatment options to find one that works. In some cases, your doctor may recommend a topical treatment plus an oral or injectable medication. Follow your health care provider’s instructions. Nail psoriasis is not yet curable, but it is usually treatable.

Nail Fungus Treatments

Common psoriasis treatments, like topical steroid creams, can worsen some fungal infections. Before trying to treat what you think is nail fungus at home, ask your doctor for help.

Treatments for nail fungus include:

• Over-the-counter antifungal creams or lotions
• Topical medications, like efinaconazole, ciclopirox, or tavaborole, applied to the affected area
• Oral antifungal drugs, like itraconazole or terbinafine
• Medicated nail polish
• Nail removal

Before deciding on a treatment plan for nail psoriasis or nail fungus, ask your health care provider about the risks and side effects. If they recommend nail removal, be patient. Nail growth is slow. A fingernail can take three to six months to regrow and a toenail closer to nine months.

For questions about skin diseases or nail health, consult a doctor specializing in dermatology.

Talk With Others Who Understand

MyPsoriasisTeam is the social network for people with psoriasis and psoriatic arthritis and their loved ones. On MyPsoriasisTeam, more than 116,000 members come together to ask questions, give advice, and share their stories with others who understand life with psoriasis and psoriatic arthritis.

Do you have nail psoriasis? Have you had nail fungus? Which treatments worked for you? Share your experience in the comments below, or start a conversation by posting on your Activities page.