Avoid using Cephalexin, or any medication that contains Cephalosporin, in animals allergic to cephalosporin or penicillin. Cephalexin, and other Cephalosporin based medications, should be used with extreme caution in pregnant and nursing animals or animals who are taking probenecid or aminoglycosides like neomycin and gentamicin. Inform your veterinarian or pharmacist about the medicines your pet is taking and be sure to administer the full treatment of the medicaiton, even if your pet has fully recovered from the infections. Over-dosage could lead to adverse side effects. Cephalexin, and other Cephalosporin based medications, are not effective in fighting infections triggered by mites, parasites, viruses or fungi. Do not give your pet their medicaiton more than directed.