The Rat Fan Club

This article is from the Rat Health Care booklet. Order one today! Check out the info at Rat Books

Skin Problems

by Debbie “The Rat Lady” Ducommun

The most common skin problem in rats is caused by itching. The rat scratches herself which creates scabs, most often on the neck and shoulders, but sometimes also on the face, chin, or forehead. These scabs are sometimes mistaken for injuries caused by other rats. The causes of itching are fur mites, an allergy, excessive dietary protein (such as fish or cat food), eczema, and a fungus infection. A bacterial infection of the skin may also be involved, but it is rarely the primary cause.

Itching also seems to be related to stress, common for eczema. It’s also possible that some rats infested with mites can keep them under control until their immune system is suppressed by stress. It’s also possible that some rats with mites eventually develop an allergy to them. If you have more than one rat with scabs, it's probable that mites are the cause.

Regardless of the cause of the itching, when the rat scratches, her back toenails break the skin which can allow bacteria to enter. As the scratches heal, scabs form and can themselves itch which causes more scratching, resulting in a vicious cycle. The first step to breaking the itching cycle is to clip the rat's back toenails. Trimming off the sharp tips reduces the amount of damage the nails do to the skin. You might need to clip the nails as often as once or twice a week. You can also put a brick or concrete block in your rats’ cage to help her wear down their toenails.

You might also apply a vitamin E cream or an antibiotic ointment to the scabs once or twice a day. Neosporin Plus contains a topical anesthetic which can be especially helpful. This treatment may be sufficient to clear up the scabs. If they recur, you need to look for another cause.

The picture below shows scabs caused by rat fur mites, which made the rat itch and scratch and damage her skin.

These two pictures below show rat fur mites on a dead rat. As the dead body cools, the mites crawl to the tips of the fur to try to catch a ride on a living rat. It is almost impossible to see the mites on a live rat. Observe that the mites are only slightly wider than the rat’s whiskers.

The picture below shows a rat with lice. On the right you can see the little brown lice themselves, and on the left, you can see the eggs, called nits, which are silvery blobs stuck to the fur.

The picture below shows a rat with such a bad case of lice, her skin formed a crust. See where I pulled off two pieces of the crust to reveal red moist irritated skin. The poor rat! She also had thinning fur on her belly and sides. Even with such a bad case of lice, this rat did not develop scabs like rats with the fur mites can.

On the left is Monty, who has an early case of mange mites on his ears. On the right is a rat with a more severe case of mange mites.

Clipping Toenails

Trimming your rat’s toenails is really quite easy to do once both you and the rat are used to it. The best tools to use are human fingernail clippers. Hold your rat on your lap facing left if you’re right-handed (reverse these directions if you’re left-handed). Press him against your stomach with your left forearm to hold him still and hold his foot in your left hand. Pull his foot backward and clip the nails with your right hand. You only need to clip off the sharp tip on the end of the nail. If you cut too much off, the nail will bleed. It’s a good idea to have some styptic powder or silver nitrate sticks on hand to stop any bleeding, but if you’re careful, bleeding rarely occurs. You can eliminate the chance of accidentally cutting a toe by holding the foot so only the nails stick out. Your fingers protect the toes.

If your rat really struggles, only do a few nails at a time. Reward him with a treat afterward. You can also distract him during the procedure by giving him a treat in the beginning.

Mite Treatment

The next thing to try is to treat for fur mites. Theoretically, if you apply a mite spray once a week for long enough, it should be able to eventually kill all the mites, but in practice this doesn’t seem to work very well. Plus rats hate the spray, and it is quite toxic and causes some rats to have a bad reaction!

Ivermectin used to work against the rat fur mites, but now they are resistant. Treatment with ivermectin will kill most of the mites and help relieve the rat’s itching, but it won’t kill all the mites and the itching will return.

You must treat all of your rats, since if one rat has fur mites they probably all do, even if they don’t all have scabs. Rats can have the mites without any symptoms.

The treatment I am currently recommending for fur mites is Revolution (selamectin) which you can get from your vet (with a prescription in the U.S.) You can also get Revolution at www.joespetmeds.com. In the UK or Australia you can order it from www.pets-megastore.com.au or 1-866-270-2303.

Your vet might want to do a skin scraping to look for the mites first, but the rat fur mites don’t live in the skin (that’s why they are called fur mites) so a skin scraping should not be done. Your vet can press a piece of tape to the rat’s parted fur and look for any mites stuck to the tape under a microscope. But this method of looking for mites can be hit or miss. Even if there are no mites on the tape, the rat can still have mites.

Revolution is a spot-on product, a liquid that is applied to the skin on the shoulders. After application, you need to distract your rats so they don’t scratch off and eat the liquid, or lick it off of each other. The liquid will dry in about 5 minutes. Only one dose is needed.

Revolution comes in tiny tubes of different sizes for different size cats or dogs. Packages of Revolution come with either 3 or 6 tubes of liquid. (If your vet treats a lot of small animals, he or she might be willing to split a package and sell individual tubes.)

Each tube costs about the same amount no matter how much Revolution it contains, so you want to figure out which tube will treat all your rats. To figure out what package to buy you will need to weigh each of your rats, total the number of pounds and multiply that by the dose (6 mg/lb). That will tell you the total number of milligrams of Revolution needed to dose all your rats.

Here’s a summary of all the packages of Revolution:

color size of pet total mg concentration

mauve up to 5 lbs 12 60 mg/ml

blue 5.1-15 lb (cat) 45 60 mg/ml

purple 5.1 10 lb 30 120 mg/ml

brown 10.1-20 lb 60 120 mg/ml

red 20.1-40 lb 120 120 mg/ml

teal (green) 40.1-85 lb 240 120 mg/ml

plum 85.1-130 lb 120 + 240 120 mg/ml

The dose for the tubes that contain 60 mg/lb is 0.1 ml/lb (10 units/lb). The dose for the tubes that contain 120 mg/ml is 0.05 ml/lb (5 units/lb.)

The amount of liquid needed per dose is quite small, and is best measured using an insulin syringe with the needle (or the whole top) broken off. Insert the syringe into the tube slowly as it will easily overflow. Once a tube is opened, it must be used within a few hours.

Here is a peer-reviewed article on the Internet about using Revolution in rats in case your vet has objections: http://www.jarvm.com/articles/Vol5Iss3/Beck%2087-96.pdf

Another treatment you can try for fur mites is ivermectin. However, I’m finding that most fur mites are now resistant to it. It might help for a while, but the problem usually comes back. It needs to be repeated once a week for at least 6-12 weeks. Most veterinarians will use ivermectin injections instead of giving it orally and will charge much more for a series of injections than you would pay to buy the ivermectin yourself from a feed store. Since the ivermectin may not work for the mites, I do not recommend paying a lot of money for treatment.

Another treatment that might work is moxidectin (another relative of ivermectin) which is available from feed stores as Quest brand horse wormer. I just learned about this product. The dose is 1 mg/lb¹³. The amount to give a 1-lb rat is 0.05 ml (5 units). The Quest product is a clear oral gel that is easy to suck into an insulin syringe (with the whole top broken off) for accurate measurement. It tastes nasty so needs to be well mixed with yummy food. Moxidectin stays in the rat’s body for a long time, so one dose should be enough to kill lice, and hopefully mites. If you try this product, please let me know your success.

I have a report that the product Frontline (fipronil) did not work for fur mites in one case. It must be used with extreme care as it is very toxic to rats if ingested. If you use it, you must be absolutely sure the rat does not eat any of it. After applying it, make sure the rat does not scratch or lick it off until the liquid dries.

Revolution also works for tropical rat mites. Ivermectin does not. I do not have carpet in my house, so if you do, you may need to also spray or bomb the carpets, but try just the Revolution and cleaning around the cages first.

Flea & Lice Treatment

If your rat has fleas, it is more important to treat your other pets and possibly also your house and yard instead of the rats.

The best treatment for lice in rats is oral ivermectin. When given at the proper dose ivermectin is very safe, but it should be given orally because in some rats when it is given by injection, it can interact with a genetic bleeding tendency and be fatal.

Ivermectin is also available in a horse paste wormer from feed stores and catalogs. A tube of horse paste costs about $12-15. The dose for the paste is 0.01 ml/lb (1 unit on an insulin syringe) which is about the size of an uncooked grain of rice. First squeeze all of the paste in the tube out into another container, such as a pill bottle, and mix all the paste up well before taking out doses to make sure the ivermectin is evenly distributed in the paste. Put the dose on a tiny piece of bread for your rat to eat. You can add butter or jam on top if your rat is reluctant to eat it plain.

You can also get injectable ivermectin, which can be given orally, from a feed store or a mail order catalog. The injectable form can be accurately measured with an insulin syringe, but only comes in 50 ml bottles which is fairly expensive. The dose is generally 1-2 units/lb.

Ivermection should not be used in pregnant rats, and only in nursing rats if the babies are over 2 weeks of age.

Other treatments that might work are Advantage, Program and Revolution. Lice eggs normally hatch in 5-6 days, so any eggs that haven’t hatched after that time are dead and harmless but will remain stuck to the hair until the hair is shed.

Allergies

The most common foods for a rat to be allergic to are peanuts and dairy products, including yogurt drops. Eliminate these items for at least two weeks to see if this solves the problem. If the problem is another allergy, or eczema, treatment with a steroid will stop the itching. You can try a hydrocortisone cream (be sure to rub it into the skin well), or ask your vet for oral predisone an antibiotic should be given with it because steroids depress the immune system). Sometimes the steroid treatment alone will clear up the problem, but if the itching returns after the treatment, you must try to identify what the rat is allergic to.

It is rare for a rat to be allergic or sensitive to most litters, other than pine or cedar shavings, but you might want to try changing your rat's litter or bedding. Because I think a rat can develop an allergy to fur mites, I recommend treating for mites if you can’t identify another allergen.

If you know your rat’s problem is an allergy, the next step is to test for further food allergies. A good testing diet is a mixture of cooked brown rice and raw millet, plus 1 teaspoon of Nutri-Cal per day. You can buy Nutri-Cal at any vet hospital. If you see an improvement in 7-10 days you then add foods one at a time to see if they cause itching. If you identify the food your rat is allergic to, then you can put her back on a normal diet, minus the offending food.

It is also possible for a rat to have eczema, which causes itching with no known cause. The treatment in this case is a topical steroid cream or shampoo, and you often have to continue the treatment for the rest of the rat’s life.

Fungus

If your rat hasn’t responded to the ivermectin or the prednisone, the only thing left is to treat your rat for a fungal infection. Like the skin scraping for mites, biopsies or skin scrapings for fungus often yield a false negative. Therefore, you must try the treatment.

The fungus infections that can grow on the skin are commonly called ringworm, because of the red ring they can cause on human skin. Ringworm is very contagious and can be passed from humans to other animals and back again. Rats who have a fungal infection of the skin don’t always show symptoms. If your rat does have a skin lesion, you can try an over-the-counter cream such as Lotrimin. Antifungal shampoos don’t seem to work.

For a rat who has widespread lesions, or for a rat who shows no skin lesions at all, you should use an oral fungicide. For griseofulvin the dose is 12-25 mg/lb twice a day for at least 4-6 weeks. Give griseofulvin with a meal that includes fat. For ketoconazole (Nizoral) the dose is 4 mg/lb three times a day for at least 3-4 weeks. With either treatment you should see improvement in 1-2 weeks. In some cases treatment may be needed for up to 3 months. Program may also be an effective treatment for fungus (veterinarians are still not sure of this.) Because fungus thrives on sugar, a rat with a fungal infection should receive only limited amount of sugar (including fruit) in his diet.

Dry Skin

While oily dandruff is normal in intact males, dry skin and dandruff can be symptom of a poor diet. If your rat is getting an adequate diet, try giving a supplement containing essential fatty acids. Dry dandruff can also occur in rats with hindquarter paralysis since they can't groom themselves normally. If the humidity in the air is too low, it usually affects the tail rather than the skin. This can prevent the dead skin cells on the tail from shedding properly resulting in patches of scaly skin and discoloration. The solution is to run a humidifier in the room.

Ringtail is a skin problem caused by dehydration that is occasionally seen in baby or hairless rats, and rarely in haired adults. Dehydration can occur if baby or hairless rats are kept on litter that is too absorbent (commonly corn cob litter) or in any rat if the water bottle malfunctions. In babies ringtail causes a constriction at the base of the tail. In adults it can cause a moist oozing sore at the base of the tail. The problem usually goes away when the rats are rehydrated, although if the problem is bad enough a baby may lose part of her tail.

The picture on the left shows a tail with excessive unshed scales which should be picked or scrubbed off. Letting scales stay like this can result in the formation of scabs, as you can see in the second picture. The picture on the right shows a rat with an infection in the end of his tail.

Hair Loss

There are two main causes of bald spots in rats. The most common is barbering, a behavior where a rat obsessively grooms itself or another rat to the point of nibbling off the hair. The result is bald patches or areas where the hair looks like its had a bad haircut. Usually there is no damage to the skin, but sometimes there can be scabs. The most common areas for self-barbering are the front legs and stomach. The most common areas for barbering another rat are on the head, face, neck, and shoulders. These bald spots are not usually symmetrical. Because this behavior doesn't usually cause any health problems, there is no reason to separate a barber from her roommates, unless you are showing your rats. Another cause of bald spots is fungus (see above.)

Another type of hair loss is a general thinning of the hair. This can occur in a rat infested with lice or tropical rat mites. Although in these cases the rat usually doesn't self-inflict scabs, constant scratching can cause general hair loss, most commonly on the back. Rex rats may tend to have thinning hair as they grow older or if they are stressed due to disease.

In some other animals, such as dogs and cats, a hormone problem can cause hair thinning, although I haven’t seen this in rats. This type of hair loss is usually seen on the flanks, hindquarters and sometimes the stomach and is usually symmetrical.

Rat Fan Club
857 Lindo Lane
Chico, CA 95973
(530) 899-0605
ratlady@ratfanclub.org