Topical 5-FU

Dr. Aouthmany, MD, FAAD
Board Certified Dermatologist

Topical 5-FU
  • Topical 5-FU is a cream that is used to treat precancerous skin lesions (actinic keratoses) and certain skin cancers. 
  • Actinic keratoses are precancerous growths that have the capacity to develop into squamous cell carcinoma, a type of skin cancer. Actinic keratoses can be treated in several ways, but they are most commonly treated with either liquid nitrogen (frozen) or topical medications: 5-FU or, sometimes, an unrelated medication called imiquimod. 
  • Apply twice a day to areas instructed.  You do not need a lot.  the treatment course is 4 to 6 weeks depending on your dermatologist recommendations.
  • You can apply the medication with your bare hands, but wash your hands after using it. 
  • Try to keep the medication away from your eyes. 
  • Generally, after a week or two of application your skin will start to look red; this is expected. As the cream destroys the precancers or skin cancers they will become red, inflamed, irritated and slightly sore. 
  • Sometimes, itching may also develop. If your symptoms are severe, call and let us know.
  • APPLY any of these ointments below 1 hour after the 5-FU application to help with relief. (Your dermatologist may have given you a prescription for topical steroid instead) 
Vaseline (petroleum jelly)
DML Forte
Cerave ointment
  • If still symptoms are severe, skip a day or more.  However, if it is not bothering you too much you should try to treat for a full 4 weeks. 
  • Avoid prolonged sun exposure while you are using this cream. If you do go out in the sun, use a broad-spectrum sunscreen.
  • Rarely the medication can cause systemic symptoms such as nausea or fatigue.
  • Once you finish the medication, the area of skin treated will be red and raw. It generally takes about 3–4 weeks for all of the inflammation to resolve. May continue to use the topical ointment.  
  • This medicine is extremely toxic to dogs and cats. Less than a gram can kill a small dog. DO NOT leave the tube where your dog or cat could get it.