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Actinic Keratoses FAQ

1. What are actinic (solar) keratoses?

Actinic keratoses (AKs), also called solar keratoses, are typically red, dry, scaly lesions that usually develop after years of exposure to the sun or indoor tanning. They are commonly seen on sun-exposed areas of the body, such as the face, arms, back of hands and on a bald scalp. The lesions typically are smaller than a pencil eraser and range in color from white scaly to reddish brown.(1)(2)

It is very important that anyone with AKs be under a dermatologist’s care or a primary care physician with experience. AKs tend to grow over time and some may become squamous cell carcinomas (skin cancer).(1) The presence of AK’s is most likely the reason your physician has recommended therapy with fluorouracil 5% (generic for Efudex®) or fluorouracil 0.5% (generic for Carac®) cream. You can typically tell by the look and feel of your skin whether the lesions have cleared by feeling, but a follow-up examination by your physician is very important.

2. How does Fluorouracil Cream work?

Fluorouracil Cream is one of the most frequently used AK treatments in the United States. It is a chemothreapy applied to the sun-damaged skin that causes temporary redness and crusting. As the skin heals, healthy skin appears.(1)

3. Will Fluorouracil Cream work?

Fluorouracil Cream is a very effective treatment; however, the patient must overcome the irritation that occurs while killing the pre-cancer cells. This is a strong treatment and some form of redness and irritation occurs in the majority of patients.(1)

Patients may take comfort in knowing that irritation is a sign that the treatment is working. If severe irritation or open-skin areas appear, call your physician for an examination or to be advised if the treatment should be stopped.

4. How should Fluorouracil Cream be used?

First and foremost, it is very important to follow the instructions your physician gave you. You should receive instructions with your prescription that detail specifically when and where to apply, how much to use for each application, and the length of therapy. You should be sure that these instructions are clear and that you or your caregiver will be able to follow them. Please contact your physician if you have any questions or if you feel you are unable to complete the therapy as prescribed.

Fluorouracil cream should be applied using your fingertips or for the 5% strength, preferably with a non-metal applicator, or a disposable glove. If the product is applied with your fingertips, special caution should be used to wash hands immediately and thoroughly after application. Always keep the product away from the eyes, corners of the nose, and mouth.

Fluorouracil cream is applied in an amount sufficient to cover the lesions. Patients typically apply 5-FU twice daily for 2 to 4 weeks.(1) However, this may vary depending on the area to be treated and the treatment’s progress.(1) We strongly believe that after 2 weeks the patients should be examined to see if continued application is needed. Application to open skin adds to potential side effects. Be sure to closely follow the directions given to you by your physician.

Fluorouracil Cream is an anti-cancer chemical and there is a potential for systemic absorption – approximately 5.98% of topical dose for fluorouracil cream, USP 5% (see prescribing information). Therefore, do not use on large areas (e.g., scalp, ears & face) at one time unless expressly recommended by your physician. Treating different parts of the face or body at different times is one method of increasing a patient’s tolerance and comfort during the treatment.(2)

5. For our patients who use a CPAP mask while treating their AK’s or basal cell carcinomas: 

It is well known by Dermatologists that occlusion of the skin adds to penetration of topical creams.(3) An example of this would be under a CPAP mask, which may increase the irritation effect of 5% 5-FU topically if used on the face. It could add to the redness and irritation under your CPAP mask. As such, we advise using the product carefully on the face if you use a CPAP mask, and potentially for a shorter time, under the direction of your Physician.

-K.L. Spear M.D., Dermatologist

6. What is the safety concern if my pet is exposed to Fluorouracil Cream?

Fluorouracil Cream USP 5% is a topical cancer medication and intended for use in humans. Please use care when applying and storing the medication if pets are around, as even small amounts can be dangerous to the animals. There have been cases of dogs ingesting the cream and dying. Keep medication safely away from children and pets. If your pet becomes exposed, consult a veterinarian immediately.

For further information, please consult this article from the FDA: “FDA Warns of Illness and Deaths in Pets Exposed to Prescription topical (human) cancer treatment: Fluorouracil”

This therapy is not indicated for women who are or may become pregnant. See our full prescribing information for Contraindications and Precautions.

Remember to wear your sunscreen and a hat, and see your physician regularly.

Make an appointment with your dermatologist and ask if Fluorouracil Cream would be right for you.

Please see full prescribing information for Fluorouracil Cream, USP 5% and Fluorouracil Cream, 0.5% for further information. Talk to your treating physician with any questions.


  1. American Academy of Dermatology. Actinic Keratosis. Accessed August 19, 2019, at—d/actinic-keratosis.

  2. Anderson NJ, Jeffes EW. New therapeutic advances: skin cancer and actinic keratoses. A Supplement to Skin & Allergy News. 2003;34(3):1-15.

  3. Fluorouracil Cream USP, 5% [package insert]. Rockledge, FL: Spear Dermatology Products; 2016.

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