My cat is still biting his tail and losing hair after flea treatment.

A flea bite can cause itching and irritation for several weeks after the fleas are controlled. The majority of a flea problem is the environment. The fleas still have to get on the cats to bite and get the medicine to die, so you can still have a flea problem without seeing fleas on the cats. IF the spots and itching persist you will need to see a vet for a culture to diagnose ring worm. To get rid of the fleas you will need to get everyone out of the house and treat the house also

Even though you don't see any fleas, your cat could still be having an allergic reaction to fleas. It only takes the bite of one flea to set off the reaction, and itchiness over the base of the tail is classic flea allergic dermatitis. However, dermatitis can be brought on by other skin parasites (mosquitoes, mites, lice), bacterial and fungal skin infections, nutritional imbalances, hormonal imbalances, and autoimmune disorders. Therefore, I recommend that you have your cat examined by your veterinarian for a full clinical work up.

If they were scratching due to fleas then it is not unusual they are still itching. The bites from the fleas will not go away overnight (imagine if you had mosquito bites, these persist for quite a time after the bite occurs) and often the die off of fleas will cause increased itching for a day or two. If the itching is severe your vet may prescribe medication to help, or if they are still itching excessively in a few days, seek veterinary care.

There is a possibility that he is irritated from flea bites at his tail and/or from the spot on. It is a well-known side effect that spot-ons can cause an itch, hair loss, irritation, but usually that irritation is gone within a few hours. Do not let him bite or lick or scratch the application location. You can put a loose t-shirt on him covering up the location or put on an e-collar. If the irritation has not subsided by tomorrow, or if Boy boy develops a wound , he will need to be seen by a veterinarian for an exam. In the meantime do not put cream or ointment onto the location where you applied the flea treatment.

Poor Spud! Continued, chronic skin issues generally indicate one of four things in cats. It indicates flea allergy, environmental allergy, food allergy or thyroid disease. You can rule out continued flea problems by using a good product such as revolution or a Cheristan. For 2-3 months, if the skin issues clear up, it was likely a few pesky fleas. Food allergies are diagnosed by feeding a special prescription hydrolyzed protein diet. Thyroid conditions are diagnosed with a blood test. Environmental allergies are the most difficult to diagnose and may require a blood test or trial of medication. Secondary infections are very common with all these conditions. It sounds like Spud is uncomfortable with the constant licking and chewing. I recommend to have him see his veterinarian for medications that will provide some relief. You can also talk to the doctor about which of the four conditions to start ruling out first. I hope this is helpful and please feel free to post any additional questions.

If the flea treatment route isn't helping another avenue you could look to is a behavioral issue such as extreme stress leading to hyperstimulation or overgrooming, which can lead to a cat grooming to the point they tear their fur out/go bald/cause bleeding hot spots. Often, treating the underlying stressor can help to reduce the incidence, but in some cases additional help such as an Elizabethan (cone) collar to stop the habit while treating the stress is also needed. You can try out something such as Feli-way plugins or collars to help reduce stress, and if that still doesn't help speak with a trainer or behaviorist in your area that can help figure out a plan. Other medical causes of stress can include food allergies, injuries from other cats, environmental allergies, and other parasites beside fleas that could be aggravating the skin. Infections from yeast or bacteria can also cause hot spots to form and can be irritating to the skin. If you haven't yet, ruling out some of these other causes may be another avenue to explore.

Thank you for using Petco Pet Education Center, formerly Petcoach! George's itching can be caused by a reaction to the fleas, a secondary skin infection, ringworm, or other skin parasites such as mites. George may need antibiotics, medicated shampoo or ointments to resolve the issue completely. I recommend having her seen by her vet, who can take a sample of the affected areas to determine what is going on. I hope this helps and that all is well with you and George!