Maybe you’ve noticed that your fingernails are looking yellow or brown or that your toenails seem thicker than usual. How do you know if these symptoms are related to nail psoriasis, nail fungus, or both?

“My doctor just looked at my nails and treated me for fungus, but it was not a fungus,” MyPsoriasisTeam member said. “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. So, how do you tell the difference between a fungal infection and psoriasis? The good news is that a few key signs can help you and your healthcare provider tell one condition from the other.

This article covers five important ways these two conditions differ, including what causes them, how they show up, and how they’re treated.

1. Nail Psoriasis Isn’t Contagious

Psoriasis is a chronic (ongoing) skin condition that often affects the knees, trunk, elbows, and scalp but can involve the nails, too. Psoriasis is an autoimmune disease. The condition develops when part of the immune system becomes overactive, leading to skin changes and sometimes psoriatic arthritis (a type that causes joint pain and swelling) and nail changes. Nail psoriasis isn’t contagious.

Fungal infections result when a fungus comes into contact with the skin or nails and finds favorable conditions for growth, such as 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

Researchers don’t yet fully understand what causes psoriasis, but certain factors can trigger flare-ups (times when symptoms get worse). Common causes and triggers of nail psoriasis 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 very common in people who have psoriasis or psoriatic arthritis. According to the National Psoriasis Foundation, about 90 percent of people with psoriasis will develop psoriatic nails at some point. 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. 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 tinea pedis (athlete’s foot)
• Wearing plastic gloves daily, such as while working
• 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.

You can’t spread nail psoriasis to other people, but the same isn’t true of fungal nail infections. If you’ve been diagnosed with nail fungus, ask your healthcare provider how to protect your friends, family, and other people from getting it.

2. Nail Psoriasis Is Unlikely To Cause an Odor

Nails that look different or change color and also have a foul odor are more likely to be affected by a nail fungus than by nail psoriasis. The unpleasant smell comes from tiny microorganisms (germs) that feed on your skin or nails. Not all fungal nail infections smell, but if there is a strong odor, it’s probably not nail psoriasis.

Nail Psoriasis Symptoms

Plaque psoriasis usually causes raised, scaly patches on the skin that can flake, itch, burn, or sting. However, psoriatic nail disease shows up differently, affecting the fingernails and toenails with its own set of symptoms.

Symptoms of nail psoriasis include:

• Pitting — Tiny dents or 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

When nails lift off the nail bed — a symptom of nail psoriasis — it can create a space where fungi can get in and grow, leading to a fungal nail infection.

Nail Fungus Symptoms

In addition to causing an unpleasant smell, a fungal nail infection can lead to symptoms such as:

• Discoloration — White, brown, or yellow patches that spread over time
• Nail plate thinning — A 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.

Not only do some symptoms of nail fungus and nail psoriasis overlap, but you can also experience both conditions at the same time. The pitting seen with nail psoriasis can be a symptom of other skin diseases, like eczema or vitiligo. White nail discoloration, called leukonychia, can indicate other health issues. Getting an accurate diagnosis is essential.

3. Nail Psoriasis Is More Common on the Fingers

Both nail psoriasis and nail fungus can affect your hands and feet, but nail psoriasis is more likely to show up on your fingernails. Nail fungus usually affects the toenails.

Researchers and doctors aren’t sure why nail psoriasis tends to affect fingernails more often. However, it’s easier to understand the connection between nail fungus and toenails.

Why Does Toenail Fungus Happen?

Fungi grow best in warm, moist, and dark places — like the inside of sweaty socks and shoes. That makes your toes the perfect spot for fungi to thrive. Unless you regularly wear gloves for long periods (like at work), your hands usually stay drier and more open to air, so they’re less inviting — unless you have a cut or crack in your fingernail that allows the fungus to enter.

If you often get toenail fungus and your skin is peeling around your toes, you might also have athlete’s foot — a common fungal infection that affects the skin.

4. Nail Psoriasis Often Affects Multiple Nails

Your healthcare provider might also consider 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

Your doctor will likely start the diagnosis process by doing a physical exam and asking about your symptoms.

If your doctor thinks you might have a fungal nail infection, they may take samples of debris from under your nail or clip part of the nail to send to a lab for testing. If they suspect psoriasis, they’ll likely check the rest of your body for other skin symptoms because of the prevalence (commonness) of psoriatic nail disease in people with other types of psoriasis.

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

5. Nail Psoriasis Treatments Target the Immune System

Even though nail psoriasis and nail fungus can look alike, they require different treatments. To manage nail psoriasis symptoms and help you feel more comfortable, your healthcare provider will likely focus on targeting the immune system and calming inflammation. For nail fungus, they’ll usually recommend topical or oral antifungal treatments — either creams you put on your nails or medicine you take by mouth.

Nail Psoriasis vs. Fungus Treatment

Nail psoriasis and nail fungus have some overlapping treatments, but certain therapies that help one condition may make the other worse. That’s why it’s important to check with a doctor who specializes in dermatology (the branch of medicine that focuses on skin, hair, and nails).

Nail Psoriasis Treatments

Your treatment options will depend on factors such as your diagnosis, severity of symptoms, and overall health, as well as whether you have psoriasis on other parts of your body. Treatments for nail psoriasis include:

• Topical steroids or other therapies applied directly to the nail or nail bed
• Oral or injected medications that treat inflammation throughout the body
• Phototherapy (light therapy) to reduce inflammation
• Laser treatments to target the nail area
• Biologic treatments that target specific parts of the immune system
• Nail removal in rare or severe cases

Treating nail psoriasis can take time and patience. You may need to try more than one approach to find what works best. In some cases, your doctor may recommend using a topical treatment plus an oral or injectable medication. Nail psoriasis isn’t curable, but it’s usually treatable.

Nail Fungus Treatments

Some common psoriasis treatments, such as topical steroid creams, can make fungal infections worse. Before trying to treat what you think is nail fungus at home, ask your doctor for help.

Treatment options for nail fungus include:

• Over-the-counter antifungal creams or lotions
• Prescription antifungal medications, both topical and oral
• Medicated nail polish
• Nail removal in more serious cases

No matter which condition you’re dealing with, always talk with your doctor about the risks and possible side effects of any treatment. If they recommend nail removal, be patient — nail growth is slow. Fingernails usually take three to six months to regrow, while toenails can take 12 to 18 months.

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 133,000 members come together to ask questions, give advice, and share their stories with others who understand life with psoriasis and psoriatic arthritis.

What does nail psoriasis look like on your fingers or toes? Have you been able to tell the difference between toenail psoriasis versus fungus? Share your experience in the comments below, or start a conversation by posting on your Activities page.