Q: My big toe got all swollen and red and very painful on one side. I went to the SHAC and they cut off part of my toenail. They told me it was an ingrown toenail. How does this happen? Is there any way I can avoid this in the future?

A: First of all, I hope you feel better now. I expect you do, because what you got was the standard treatment and what you needed was relief. Your problem is quite common — we probably see a couple of these every month at SHAC.

To explain what happened to you, let me begin with how nails grow. Fingernails and toenails are formed at the base of the nail, under the cuticle, in the light-colored part called the lunula. The word “lunula” comes from the same word root as “lunar.” Look at the base of your thumbnail: see that crescent moon? New nail cells are laid down in the lunula every day, and as that happens the older cells get pushed up the nail bed toward the tip of your finger or toe. While the nail plate is in contact with your finger or toe, it is nourished by the nail bed underneath it. When it grows out beyond the end of the nail bed, it dies and turns white and you cut it off.

I hate to say it, but ingrown nails are usually caused by improper nail trimming. You can blame your pedicurist if you have one. Toenails should be cut straight across, in a straight line, and not too short. When you are done, there should still be white nail showing, and the white part should extend beyond the corners where the nail meets the toe.

If you cut them curved and short, that can leave a little sharp piece of nail unnoticed right in the corner. As the nail continues to grow, pushed up from below, this little shard dives into the tender flesh at the tip of your tootsie. More growth, more diving, more damage. The tissue gets swollen in response to this injury, the blood supply is compromised by the swelling, and, given all the germs on our skin, an infection is almost inevitable. That is what usually tips the balance from putting up with it to coming in to the clinic for help: Infected ingrown nails, as you experienced, are quite painful.

The reason we cut off part of your nail is twofold. One, the treatment for a localized infection like that, or an abscess, is to drain it. You have to give the pus an outlet. Two, by excising part of the nail, we remove the offending shard and allow your toe to heal while a new smooth nail grows back in. This will take several weeks. You will be pleasantly surprised to find that the newly exposed nail bed is tougher than you might think and after a few days it doesn’t hurt anymore.

If the skin on one side of your toe tip gets swollen and tender, you might be getting an ingrown nail. You may be able to manage this at home before it gets too deep and infected. First of all, resist the temptation to cut the nail more. You will only make it worse if you do this. Instead, try the following: soak your foot in warm water twice a day for 10 minutes. After you soak, take a cotton swab and gently but firmly push that tender flesh away from the nail. You are trying to free that diving shard, and give it room to grow out into the air instead of into your toe. If that doesn’t work, we’ll probably be seeing you in the clinic.

The procedure for relieving an ingrown nail goes like this. First, we numb up the whole toe by injecting an anesthetic at the base of your toe where the nerves are. I won’t lie — this hurts — but once the medicine takes effect your whole toe is numb and you can have a nap while we cut the nail lengthwise, from tip to base, in a straight line about a third of the way across the nail. We then loosen the affected part of the nail, freeing it up from the abscess and from the nail bed, and pull it off. Then you tell us all your secrets or we pull off the rest.

I’m kidding, of course.

Toenail surgery and other acute and chronic problems can be managed at your local SHAC. Call (505) 277-3136 for an appointment.

Peggy Spencer is a student-health physician. She is also the co-author of the book “50 ways to leave your 40s.” Email your questions directly to her at pspencer@unm.edu. All questions will be considered anonymous, and all questioners will remain anonymous.