Ingrown toenails develop when the edge of the nail plate loses its normal fit in the groove along the side of the toe and starts growing into the surrounding skin. The nail essentially becomes a foreign body, piercing the soft tissue and triggering an inflammatory response that causes the redness, swelling, and pain you feel. Several everyday habits and physical factors set this process in motion, and most of them are preventable.
How the Nail Actually Grows Into Skin
Your toenail sits in a groove of skin on each side called the nail fold. Normally the nail slides forward as it grows without disturbing this groove. But when something disrupts that fit, a sharp sliver or spicule of nail forms along the edge. That spicule gradually gets driven deeper into the soft tissue with every step you take. Your body recognizes the embedded nail fragment the same way it would recognize a splinter: it launches an inflammatory response, flooding the area with fluid and immune cells. That’s what produces the swelling, tenderness, and sometimes pus that characterize an ingrown toenail.
Cutting Your Nails the Wrong Way
The single most common trigger is trimming your toenails in a curved shape instead of straight across. When you round off the corners, you can inadvertently create tiny barbs or spicules along the nail edge. Those fragments anchor themselves into the surrounding skin, and as the nail continues growing forward, they get pushed deeper. Cutting nails too short compounds the problem: the compressed skin of the toe can rise up around the shortened nail, and when the nail regrows it has nowhere to go but into that skin. A good rule is to trim straight across, leaving the nail roughly level with the tip of the toe.
Shoes That Squeeze Your Toes
A toe box that’s too narrow or too short forces your toes together and pushes the skin of the nail fold up against the nail edge. Over time, this constant pressure can cause the nail to break or change direction, starting the cycle of inflammation. Pointed shoes are particularly problematic because they funnel all five toes into a triangular space. High heels shift your body weight forward onto your toes, increasing the downward and lateral pressure on the big toenail specifically. Even shoes that fit well overall can cause trouble if the toe box doesn’t allow your toes to spread naturally when you push off while walking.
Genetics and Nail Shape
Some people are simply born with nails that curve more sharply from side to side. In a condition called pincer nail deformity, the edges of the nail roll inward like a tube, pressing directly into the skin on both sides. This trait can run in families and is linked to certain genetic syndromes. If you’ve dealt with ingrown toenails repeatedly despite trimming carefully and wearing roomy shoes, your inherited nail shape is likely a contributing factor. The curvature tends to worsen with age, which is why some people develop chronic ingrown nails in their 40s or 50s after decades without issues.
Sports and Repetitive Foot Trauma
Athletes, particularly soccer players, runners, and ballet dancers, face a heightened risk because of the forces their feet absorb. Kicking motions slam the nail plate against the front of the shoe. Running creates repetitive downward pressure on the big toe, which bears a large share of your body weight during push-off. The big toe also rotates slightly inward each time you stand and then shifts back when you lift your foot, creating a side-to-side movement that encourages the lateral nail edge to dig into skin.
Sweating inside athletic shoes softens the skin of the nail fold, making it easier for even a small nail spicule to puncture it. And within a tight shoe, the second toe often presses against the outer edge of the big toenail, adding yet another source of lateral pressure. Stubbing a toe or dropping something heavy on it can also damage the nail matrix (the tissue that produces the nail), causing it to grow back with an irregular shape that’s prone to ingrowing.
What Happens If You Ignore It
An untreated ingrown toenail doesn’t just hurt. The break in the skin creates an entry point for bacteria. The most common culprits include Staphylococcus (including antibiotic-resistant strains) and Streptococcus, though several other bacterial species can move in. Signs that infection has taken hold include increasing redness that spreads beyond the nail fold, warmth, pus, and pain that throbs even when you’re off your feet. A greenish discoloration in the nail bed points to a Pseudomonas infection specifically.
For most healthy people, an infected ingrown toenail is painful and inconvenient but manageable. For people with diabetes, the stakes are much higher. Diabetic neuropathy can dull sensation in the feet enough that an ingrown nail goes unnoticed until infection is well established. Poor circulation slows healing and allows infection to spread to surrounding tissue or even bone. In severe cases, uncontrolled infection from something as small as an ingrown toenail can lead to gangrene or require amputation.
Mild Cases: What You Can Do at Home
If the nail is only slightly embedded and there’s no sign of infection, soaking the foot in warm water for 15 to 20 minutes a few times a day can soften the skin enough to relieve pressure. After soaking, you can gently lift the nail edge and place a small piece of clean cotton or dental floss beneath it to encourage the nail to grow above the skin rather than into it. Wear open-toed shoes or sandals while the area is tender. If there’s no improvement within a few days, or if you notice pus, spreading redness, or significant swelling, it’s time for professional treatment.
When the Nail Needs Medical Treatment
For moderate to severe ingrown toenails, or ones that keep coming back, a minor procedure is the most reliable fix. The most common approach is partial nail avulsion: a podiatrist or doctor numbs the toe and removes the strip of nail that’s digging into the skin. On its own, this relieves the immediate problem but the nail can regrow into the same position.
To prevent recurrence, the exposed nail matrix (the root tissue that produces that strip of nail) is destroyed using a chemical agent, most often phenol. This combination, called partial nail avulsion with phenolization, has a recurrence rate between roughly 1% and 4% over follow-up periods of six months to nearly three years. That’s a success rate above 95%. A 2012 Cochrane review confirmed that surgical approaches outperform nonsurgical treatments for preventing recurrence. If the matrix isn’t fully destroyed during the procedure, the ingrown portion of the nail can grow back, so completeness of the matrixectomy matters.
Recovery from partial nail avulsion is straightforward. The toe is sore for a few days, and you’ll need to keep the area clean and bandaged while it heals. Most people return to normal shoes within one to two weeks, though full healing of the nail bed takes longer.
Preventing Recurrence
Once you’ve had one ingrown toenail, your risk of getting another is higher, especially if your nail shape or foot mechanics contributed. A few habits reduce that risk significantly. Trim nails straight across rather than rounding the corners, and avoid cutting them shorter than the tip of the toe. Choose shoes with a wide, deep toe box that lets your toes move freely. If you play sports that involve kicking or running, make sure your athletic shoes fit properly and aren’t compressing the sides of your big toe. Keeping your feet dry helps too, since moisture softens the nail fold and makes penetration easier. If your nails naturally curve sharply inward, regular visits to a podiatrist for professional trimming can catch a problem before it becomes painful.