My rats were fighting and one of them got bitten. It looks quite bad. What can I do for him?
With rats, wounds generally look worse than they really are. They very rarely require intervention - though their teeth are impressive, they also have thick fur and skin. Occasional fighting is normal for rats; if it gets more frequent, or it's a case of one rat picking on another, then you may have to investigate further.
Generally, you can leave a rat to deal with his own wounds, they are exceptionally fast healers. If he has an open wound, he needs to be kept away from others in a spotless cage until he heals (a day or two). Some rats, especially the more submissive ones, can get psychologically traumatized by a fight, so be sure to offer him comfort if he wants it, and be careful when putting him back with the other rats.
If it is an open wound, but not bleeding, you actually don't need to do anything, beyond check he is keeping it clean. If you think he's in pain (fur puffy, teeth chattering) you can give him some ibuprofen, as instructed here. "The dose is 15-60 mg/lb 2-4 times a day. Lower doses are for analgesia, higher for inflammation." Do not give ibuprofen if your rat is elderly, as it can interfere with kidney function, or if your rat is bleeding. More on this later.
from the ratfanclub.org
The feet, ears, tail and mouth all have a considerable blood supply, and injuries to these areas can cause profuse bleeding. The first step to stop the bleeding is to apply direct pressure for two minutes. If the bleeding continues, put some flour in a small container and press the bleeding area into the flour, or press some flour onto the wound. The flour will help the blood to clot. Cornstarch can also be used, as well as a commercial product to stop bleeding. Another thing to try is holding ice against the injury. The cold will reduce the blood flow.
If the injury is a severed toe or tail tip, you may have to apply a tourniquet. Tie string as close to the end of the extremity as possible. Tighten the tourniquet until the bleeding slows to an ooze. Do not tighten the tourniquet too much, or you could cause additional damage. Remove the tourniquet after 20 minutes to see if the bleeding has stopped, or can now be stopped using the other methods. If not, replace the tourniquet and take your rat to the vet. If a toenail is bleeding, the best way to stop it is to use styptic powder or a silver nitrate stick. Flour or cornstarch can also be used like styptic powder. Press some into the end of the nail.
After a wound to a toe, it’s common for the toe to swell quite a bit and turn red. It’s not usually necessary to treat this condition and after a week or two, the toe will heal. If you like, you can give the rat an anti-inflammatory such as ibuprofen to help bring down the swelling.
Ibuprofen interferes with blood clotting, so if your rat has a severe injury with profuse bleeding, you do not want to use ibuprofen that day. For pain you can use acetaminophen (Tylenol) at 90-140 mg/lb every 4-12 hours. Choose the dose according to the severity of the pain and possible length of use, with lower doses for repeated use. Overdoses can damage the liver.
More here under the 'Wounds and Bleeding' section.
If the bleeding does not stop, contact a vet for more treatment.