Nail Fungus Under Acrylic Nails: Signs and What to Do
Short answer: Acrylic nails do not directly cause fungus, but a lifted or damaged acrylic can leave a gap where moisture and microbes collect against the natural nail. If you see white, yellow, brown or green discoloration under an acrylic, or the nail lifts, have it looked at. A green-black patch is often a bacterial stain rather than fungus, and only a lab test can tell them apart.
Key takeaways
- Fungus and bacteria can both discolor a nail under acrylics; the colors overlap, so guessing is unreliable.
- Lifting, gaps and trapped water are the usual starting points; keep acrylics intact and dry, and have lifted ones fixed rather than ignored.
- You cannot treat the natural nail through an acrylic; it generally has to come off for a clinician to examine and treat the nail.
- A dark streak or a spot that does not look like a bruise needs a skin specialist, not a salon fix.
In this guide
Can acrylic nails cause nail fungus?
Not by themselves. The American Academy of Dermatology says nail fungus enters through a tiny opening in the skin or nail and that dirty nails alone do not cause it. The AAD page does not discuss artificial nails. What artificial nails can change, in principle, is the environment: if the acrylic lifts, chips or separates from the natural nail, a small pocket forms. Water, soap and microbes can get in and stay there, and a damaged nail plate is easier for infections to reach.
Experts do not all agree on how much moisture alone explains the problem; some salon-training sources say it is not the only factor. What most agree on is that damage, lifting and poor hygiene (shared or unclean tools) are the practical risks. See also is nail fungus contagious?.
Signs of a problem under acrylics
| What you see | Could be | Notes |
|---|---|---|
| White or yellowish patch, thickening, debris under the nail edge | Fungal nail infection | The AAD lists a color change on part of the nail, brittleness, debris under a discolored nail, and lifting. |
| Green, blue-green or black-green patch, often with lifting | Bacterial stain (Pseudomonas, “green nail”) | Often follows trapped moisture under a lifted nail; needs a clinician to confirm. |
| Brown or black spot, often after a knock | Bruise or blood under the nail | Grows out with the nail; see bruised nail vs fungus. |
| Red, swollen, tender skin at the nail fold | Nail fold inflammation (paronychia) | Common with wet hands; may need medical care. |
| A dark streak or band that is new or growing | Needs a skin specialist | Do not wait; see below. |
Because fungus and bacteria both discolor the nail, and because the acrylic hides part of the nail, you cannot reliably identify the cause by color. For the usual colors fungus causes, see what nail fungus colors mean.
Fungus or “greenies”?
Green discoloration under artificial nails is often a bacterial stain, which clinicians call green nail syndrome. It is associated with the bacterium Pseudomonas aeruginosa colonising the space between a damaged nail plate and the nail bed (Patient Care). Because it is a bacterial problem, antifungal treatment would not be the right approach, and the usual management is different. That is a reason to have a clinician look at it instead of trying nail-fungus products from the internet.
Other causes of green or dark spots exist, including dyes or polish stains and, rarely, other infections. A clinician can examine the nail and send a sample if needed.
Should I remove the acrylic?
If the natural nail underneath looks discolored, lifted or sore, the acrylic usually needs to come off so the nail can be examined and so any treatment can reach it. Topical antifungal products cannot do their job through a layer of acrylic. The practical steps are:
- Have a clinician check the nail, ideally before reapplying any enhancement. A nail sample can be tested to see whether fungus is present.
- If you remove it yourself, go gently: forcing off a lifted acrylic can tear the nail bed and make an infection more likely. A trained nail technician with clean tools or a clinician is a safer route.
- Do not cover discolored nails with fresh acrylic or polish to hide them; see nail polish and nail fungus.
- If you have diabetes, poor circulation or a weakened immune system, see a doctor or podiatrist rather than waiting; the NHS lists these as reasons to see a GP.
Treatment: what the evidence says
Once fungus is confirmed, the AAD says prescription medication is needed, applied to the nail or taken by mouth, and that it usually takes months. Fingernails grow faster than toenails, so clearing is typically quicker than for toes, though the nail stays discolored until it grows out. The NHS says pharmacy antifungal nail paints are used daily or weekly for 6 to 12 months and that tablets are used if those do not work, with a liver blood test sometimes needed.
For the differences between fingernail and toenail infections, see fingernail fungus vs toenail fungus. For options and how they compare, see the best toenail fungus treatments, which also applies to the main medicines.
What to expect at an appointment
A GP, dermatologist or podiatrist will look at the nail and the surrounding skin and ask how long the change has been there, whether you have had a knock or injury, what products you have used, and about your health conditions and medicines. If fungus is suspected they may take a small clipping or scraping to send to a laboratory, since the NHS notes a sample may be tested to identify the type of infection before tablets are prescribed. Results usually take some time, so it helps to avoid starting a home product that could confuse the picture.
Bring the information that helps most: when you first noticed the change, when the acrylics were last applied and removed, and a list of everything you put on the nail. A phone photo taken before any removal can help the clinician see what the nail looked like under the acrylic. If you have a nail technician you trust, ask them what they saw too.
Salon and home hygiene that lowers the risk
- Choose a salon where tools are cleaned and disinfected between clients (ask how, and look for sealed single-use files and buffers).
- Do not share nail clippers, files or towels (AAD).
- Have lifting or chipped acrylics fixed promptly instead of leaving a gap.
- Keep nails short and dry; dry well after washing hands or showering.
- Treat athlete’s foot promptly if you also have it; it can spread to the nails.
- Give nails a break from enhancements if the natural nail looks thin, brittle or discolored.
Related: if infections keep returning, our page on why nail fungus keeps coming back goes through the usual reasons. Some readers also look at a paid nail-care and diet guide for recurrence, Overcoming Onychomycosis; it is a support plan, not a treatment, and our review explains what it contains and where it oversells.
Get a skin specialist to look at it promptly if
you notice a new brown or black streak or band in the nail, or a dark spot that is not a bruise from a knock (the AAD says any new dark band warrants an appointment with a board-certified dermatologist); darkening of the skin next to the nail; the nail lifting or splitting; a bump under the nail; pain, swelling, pus or spreading redness; fever; or if you have diabetes, poor circulation or a weakened immune system.
Questions to ask your doctor or clinician
- Is this fungus, a bacterial stain, a bruise or something else? Can you take a nail sample?
- Should I leave the acrylics off while we treat or investigate?
- Which treatment suits me, given my other medicines and health conditions?
- How long until I can safely have enhancements again?
- Is the dark mark on my nail something we should check more closely?
Frequently asked questions
Can you get nail fungus from acrylic nails?
Acrylics do not directly cause fungus, but lifting or damage can create a gap where moisture and microbes collect, and a damaged nail is easier to infect. Unclean tools are another risk.
Is green under an acrylic nail fungus?
Often it is a bacterial stain (Pseudomonas, sometimes called green nail syndrome), not fungus. A clinician can tell the difference, and the treatment is different.
Do I have to take the acrylic off to treat fungus?
Usually yes. Topical treatments cannot reach the natural nail through acrylic, and a clinician needs to see the nail.
How long does it take for a fungal fingernail to clear?
It depends on the nail and treatment. The AAD says treatment usually takes months, and the nail stays discolored until healthy nail grows out.
When is a dark mark under a nail an emergency?
Any new dark band or spot that is not a bruise from a knock should be seen by a dermatologist soon. Do not wait for it to change.
Related reading
- Fingernail fungus vs toenail fungus
- Can you wear nail polish with nail fungus?
- Nail fungus color: what it means
- Bruised nail vs 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
- Patient Care Online: green nail syndrome https://www.patientcareonline.com/view/green-nail-syndrome
- Merck Manual (consumer): chronic paronychia https://www.merckmanuals.com/home/skin-disorders/nail-disorders/chronic-paronychia
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.
