Actinic cheilitis (AC) is a lip inflammation caused by long-term sunlight exposure. It usually appears as very chapped lips, then may turn white or scaly. AC may be painless, but it can lead to squamous cell carcinoma if left untreated. Squamous cell carcinoma is a type of skin cancer. You should see a doctor if you notice this type of patch on your lip.

AC most often appears in people over 40 and is more common in men than women. People who spend a lot of time in the sun are most likely to develop AC. So if you’re often outside, you should take precautions to protect yourself, such as wearing lip balm with SPF.

The first symptom of AC is usually dry, cracking lips. You might then develop either a red and swollen or white patch on your lip. This will almost always be on the lower lip. In more advanced AC, the patches might look scaly and feel like sandpaper. You might also notice that the line between your lower lip and skin becomes less clear. These discolored or scaly patches of skin are almost always painless.

AC is caused by long-term sun exposure. For most people, it takes years of intense sun exposure to cause AC.

People who spend a lot of time outside, such as landscapers, fishermen, or professional outdoor athletes, are most likely to develop AC. People with lighter skin tones are also more likely to develop AC, especially those who live in sunny climates. If you burn or freckle easily in the sun, or have a history of skin cancer, you might also be more likely to develop AC. AC most often affects people over 40 and more commonly appears in men.

Some medical conditions can make it more likely that you’ll develop AC. People with weakened immune systems have a higher risk of developing AC. They’re also at an increased risk for AC leading to skin cancer. Albinism can also increase the risk for AC.

In the early stages, AC might just look and feel like very chapped lips. If you notice something on your lip that feels scaly, looks like a burn, or turns white, you should see a doctor. If you don’t have a dermatologist, your primary care doctor can refer you to one if necessary.

A dermatologist is usually able to diagnose AC just by looking at it, along with a medical history. If they want to confirm the diagnosis, they might do a skin biopsy. This involves taking a small piece of tissue from the affected part of your lip for lab analysis.

Because it’s impossible to tell what AC patches will develop into skin cancer, all AC cases should be treated with medication or surgery.

Medications that go directly on the skin, such as fluorouracil (Efudex, Carac), treat AC by killing the cells in the area the medication is applied to without affecting normal skin. These medications are usually prescribed for two to three weeks, and can have side effects such as pain, burning, and swelling.

There are several ways for a doctor to surgically remove AC. One is cryotherapy, in which your doctor freezes the AC patch by coating it in liquid nitrogen. This causes the affected skin to blister and peel off, and allow new skin to form. Cryotherapy is the most common treatment for AC.

AC can also be removed through electrosurgery. In this procedure, your doctor destroys the AC tissue using an electric current. Electrosurgery requires local anesthetic.

If AC isn’t treated, it could turn into a type of skin cancer called squamous cell carcinoma. While this only happens in a small percentage of AC cases, there is no way to tell which will turn into cancer. Therefore, most cases of AC are treated.

AC can develop into skin cancer, so it’s important to see a healthcare provider if you spend a lot of time in the sun, and your lips start to feel scaly or burned. Treatment is usually effective at removing AC, but it’s still important to limit your time in the sun or take precautions to protect yourself. Be aware of any changes in your skin and on your lips so that you can catch AC early. Learn more about skin cancer and how to protect yourself.

Staying out of the sun as much as possible is the best prevention for AC. If you can’t avoid long-term sun exposure, there are steps you can take to protect yourself from developing AC. These are similar to ways to protect yourself from sun damage in general:

  • Wear a hat with a wide brim that shades your face.
  • Use lip balm with an SPF of at least 15. Put it on before you go into the sun, and reapply it often.
  • Take breaks from the sun when possible.
  • Avoid being outside in midday, when the sun is strongest.