Aspirin can affect dogs as much as it affects humans. It causes renal failure and affects the circulatory system. However, if you give your dog the right dosage it’ll alleviate pain, reduce fever* and inflammation. Make sure you take your dog's temperature with thermoPet, the only non-contact dog’s thermometer I know of. Ask your vet about the right dosage to give to your dog. Aspirin can be very toxic. Some symptoms might include anxiety, blood vomiting, diarrhea, loss of appetite, extreme thirst, etc. Have a watchful eye if your dog shows any of these symptoms or you suspect your dog has aspirin poisoning. Keep aspirin out of your dog’s reach. Don’t ever leave your purse on the floor if you have any medications inside.

* http://www.sanomedics.com/thermometers/dog/