A loose nail is where the nail comes away or falls off, and it is also sometimes known by the medical term onycholysis. It describes the process where the nail separates from the skin underneath it, which is called the nail bed. It can either partially come off or fully come away at which point the nail will fall off. The part of the nail that has come away from the bed will look white and opaque. It can be quite disconcerting however it is common and isn’t usually a sign of anything serious. In most cases, the nail will likely grow back although be prepared as this is a slow process!
The most common cause of a nail falling off is trauma. This can be a high force trauma such as dropping something heavy on your nail or low-level trauma over a length of time such as repeatedly wearing shoes that are too small. Other causes are very broad and include genetics, medication and skin conditions. A change in your body's normal state can also result in loose nails for example pregnancy, changes in your thyroid function, conditions such as diabetes and other autoimmune conditions (where your body's own immune system attacks itself). Certain medications and some nail products can also contribute to the occurence. In an extremely small number of people, onycholysis can be a symptom of cancer although in the majority of people this is not the cause.
This really depends on what the cause is and how severe it is. Once a nail has detached from the nail bed it cannot reattach, so it is mainly about preventing more harm to the nail and treating any underlying cause. Keep the area as clean and dry as possible. Carefully trim down the nail, leaving any nail that is still attached with a margin, making sure not to damage the nail or nail bed any further. A podiatrist can help with this. Protect any remaining nail as much as you can, by avoiding things that could cause any further damage.
If the nail bed is not damaged and any underlying cause or that cause has been treated then the nail should grow back. It is unfortunately a very slow process. Fingernails can take an average of 6 months to grow back completely for toenails it's at least twice as long.
If you have loose nails and have not had trauma to the nail then it is best to get it checked out with your doctor to see if there could be an underlying cause. Depending on what they find on their assessment, they may send off nail clippings to look for any infection and also blood tests to check for any underlying cause. If you have had trauma or injury to the nail, it is best to visit a podiatrist to check you have not damaged the nail bed or nail matrix. Any signs of infection which include redness, swelling and increasing pain means you should be assessed by your doctor.