Aldara FAQ

Aldara frequently asked questions for owners

Treating equine sarcoids

  1. How can I get imiquimod for my horse?
    Your veterinarian can prescribe Aldara™ after he/she sees your horse. You must have a prescription to obtain imiquimod. Imiquimod is available from most human pharmacies under the trade names of Aldara, Zyclara and Beselna. Generic imiquimod is currently available in Canada and may be available in the USA soon if not already. Price shopping is recommended. Online pharmacies tend to have lower prices. Ask your pharmacist if they have a discount program for veterinary patients!
  2. How does it work?
    Aldara™ stimulates the horse's own immune system to kill off the tumor. This does mean that you will see signs of inflammation. Signs include swelling, oozing, redness, and tenderness. In other words, the tumor often looks worse before it gets better.
  3. What are the side effects?
    The most common side effects are swelling, oozing and pain when cleaning the site. Softening the crusts with baby oil prior to cleaning may help. These effects are due to the action of the drug on the tumor and are necessary for it to work. Side effects are usually manageable. Phenylbutazone can be used to decrease the pain associated with cleaning the treatment site.
  4. Do I need to wear gloves?
    We generally recommend wearing gloves but it isn't really necessary. Just wash your hands after application.
  5. How often do I use it?
    Most horses are treated three times weekly (MWF or TuThSat). If the horse seems to be too painful with this level of treatment, you can decrease the frequency to twice weekly or your veterinarian can prescribe phenylbutazone.
  6. How long do I need to treat?
    Many horses are showing a response in 2 months but most will still need treatment for an additional 2-4 months. To determine if the tumor is gone, clean off the scabs and crusts very well. Softening the crusts with baby oil before cleaning may help. If you see any pink shiny bumps, you should continue treatment. Flat sarcoids are harder to monitor. For this kind you may want to stop treatment after 2-4 months and recheck it 30 days later to see what areas need further treating.
  7. Will it change my horse's appearance?
    Most owners feel that the cosmetic result is good. Scarring may be present with changes in the pigmentation of the skin (darker or lighter). There may be thinning of the hair for awhile. White hairs are possible but don't seem common.
  8. How expensive is it ?
    That depends upon the size of the sarcoid. For example, for a small size tumor it would cost about $100.00 for a month treatment. Aldara™ treatment is comparable in cost to most other sarcoid remedies but doesn't require a trip to a specialty clinic and seems to be more effective in most horses.
  9. My horse doesn't seem to be responding. When should I give up?
    If there is no change after 2 months or is rapidly growing in size, it probably isn't responding. If the tumor looks somewhat worse at 2 months, that is actually a good sign that it is working. Large tumors may need to be debulked (reduced in size using surgery) or treated with something else first to decrease tumor size (tumors in this study were not debulked so we can't recommend a particular protocol).  It is important to remove all the crusts prior to each treatment so that the drug is actually reaching the tumor. If your horse won't let you clean the area well, you may need additional assistance or sedation. Talk to your veterinarian about options.
  10. Does it matter what size the tumor is or where it is?
    Some locations are more sensitive. Tumors around the eyes, ears and perineum may be harder to clean prior to each treatment. You may need to work with your veterinarian if your horse has tumors in areas that are hard to clean.  Very large sarcoids would require more drug and it may be difficult for the drug to reach the tumor base. We did not debulk (reduce in size by surgery) tumors in this study so we don't know how surgery alters the drug's effectiveness. Surgery can irritate sarcoids and make them grow faster, so any surgery should also be combined with a second type of treatment.
  11. If my horse has lots of tumors, do I have to treat each one?
    Probably. There are occasional reports of Aldara working on other warts or tumors even without direct application but these are rare. Mostly it works on the tumor to which it is applied.
  12. Can I use it if my horse is pregnant?
    Aldara™ has been used on pregnant horses. As it is a topical medication, it appears safe for use even in pregnant and nursing mares. However, if the foal rubs on the sarcoid, it may get Aldara™ on its own skin. We have seen signs of irritation on these foals. You may want to wait on treatment until the foal is weaned if the sarcoid is in an area it can reach.
  13. Will Aldara ™ work on other tumors?
    In people, Aldara™ is useful for other tumors, including basal cell carcinomas and squamous cell carcinomas. We suspect it may be useful in horses, as well, but the studies have not yet been done. It will be important to evaluate the appropriate treatment frequency and duration for the other diseases. Researchers at the University of Minnesota and the University of California - Davis are also studying Aldara™ for its usefulness in aural plaques in horses and investigating its use in eye squamous cell carcinoma.
  14. If the sarcoid completely resolves with Aldara ™ treatment, what is the chance for recurrence?
    The chance for recurrence is unknown at this time. There are no long-term follow-up studies. However, in one study, few horses were followed up for 18 months without recurrence.
  15. My veterinarian wants more information. Where can I send him/her?
    See our Veterinarian Instructions for Aldara or have him/her call or email the UMN researcher:

Dr. Erin Malone
612-625-4762 (office)
612-625-6700 (Large Animal main office)
[email protected]

Treating aural plaques

  1. What are aural plaques?
    Aural plaques are whitish plaque-like lesions on the inner surface of the ear of horses. They are often scaly and may be flat or slightly raised. They are often in both ears but don’t have to be.
  2. What kinds of problems do they cause?
    Many aural plaques seem to cause no problems and are just a cosmetic issue. Others seem to lead to ear sensitivity, difficulty bridling, head shyness and maybe even head shaking.
  3. How do horses get them?
    The plaques seem to be caused by a wart virus and are likely spread by biting flies.
  4. What do I do about them?
    Often nothing. Typically they progress very slowly. If your horse seems to be bothered by touching his ears, you may consider having them treated. Protecting the ears from biting flies can help.
  5. How do you treat them?
    Many treatments have been tried to remove the aural plaques but none have been shown consistently effective. Recent research at the UMN suggests imiquimod (Aldara™) can help clear the aural plaques and lessen the ear sensitivity. 
  6. How does Aldara™ work?
    This drug works by stimulating a local inflammatory response and encouraging the body to rid itself of the plaque.
  7. How do I get Aldara™?
    Aldara™ is a human product and is available through human pharmacies via prescription from your veterinarian. We recommend price shopping until a generic is readily available. The drug has been patent protected. Average cost in our area is $250/ box of 12 packets (lasts ~ 2 months).
  8. How do I use Aldara™?
    Aldara™ is a cream that is applied as a light layer to any area affected by aural plaques. We recommend treating 2-3x every other week (eg MWF, week off, MWF). We generally treat for 3 months and then reevaluate the ears to see if the plaques are gone. It is easiest to recheck the ears when the inflammation is down (wait one week after the last treatment before attempting to check).

    All plaques must be treated. Aldara™ does not get absorbed and only works locally.
  9. What are the side effects?
    Aldara™ creates a strong local inflammatory response. This creates redness, swelling, and oozing. The horses don’t seem affected between treatments and don’t seem to resent application of the cream (eg it doesn’t burn). However, the crusts and gunk that develop need to be removed before new cream is applied or the cream won’t reach the plaques. This part hurts if the ear is inflamed due to treatment or if the crusts are stuck to the hair. Sedation is often required. Softening the crusts with baby oil prior to cleaning may help. Treatment is easier if your veterinarian can assist you and if the hair is clipped from the areas each month. 

    Apply Aldara™ only as a thin layer. Thicker layers of cream are not needed and may cause more skin irritation.

    Due to the lack of absorption, Aldara™ seems to not affect the rest of the horse and has been used safely in pregnant mares.
  10. Won’t the horses be more head shy after treatment?
    You would think so. However, those horses that were irritated by their ears prior to treatment actually seem improved (less head shy, less ear sensitive, easier to bridle) than they were before. Luckily they seem to forgive us!
  11. Do I need to wear gloves?
    Aldara™ has minimal effects on normal skin. Just wash your hands after applying.
  12. Can I prevent aural plaques?
    We don’t think so at this time. Aural plaques are a very common problem and many horses are affected to some degree.
  13. My veterinarian wants more information. Where can I send him or her?
    See our Veterinarian Instructions for Aldara™ or have him/her call or email our researcher:

Dr. Erin Malone
612-625-4762 (voice mail)
612-625-6700 (Large Animal main office)
[email protected]