Why is a stray cat skinny, losing hair, and vomiting food and hairballs?

How lovely of you to look after this stray! There are a number of things that could cause him to lose weight, such as intestinal worms, diabetes, kidney disease, or hyperthyroidism to name a few. He could also possibly have fleas. It's important to make sure your cats are up to date on their flea treatments and deworming treatments. As for the stray, I would take him into the SPCA if you don't want to assume financial responsibility for him. They can get him the veterinary attention he needs and find him a home. Otherwise, you can take him into the vet yourself :-)

He is probably suffering from severe mange, he could possibly be suffering from some other infection as well, you will need to take him to the vet ASAP in order to get it checked and treated, he will need several injections in order to treat these conditions.

Cats who are thin despite eating well who also have areas of baldness can be suffering from an endocrine disease called hyperthyroidism. I recommend getting his thyroid levels tested by a veterinarian who does this type of testing.

Thank you for using Petco Pet Education Center, formerly Petcoach! Vomiting in cats can be caused by hair balls, intestinal parasites, toxin ingestion, or even foreign body obstructions of the intestines. These signs can be unrelated to the hair loss, which may be caused by certain infections and hormonal or behavioral abnormalities. I recommend having Zimba seen by a vet if he continues to vomit or develops diarrhea or has a loss of appetite/energy. His area of hair loss should also be evaluated, as it may be caused by a fungal infection that can even be transmitted to humans. I hope this helps and that all is well with Zimba!

Older cats like your kitty often get an overactive thyroid which will show weight loss, a really fast heart rate, sometimes vomiting, and more vocalisation than usual. Some cats get skittish as well. Hyperthyroidism can actually cause heart problems and mask kidney disease. Hyperthyroidism is easily diagnosed with a clinical exam and a little blood test and there are various treatments available, varying from Methimazole transdermal ointment or tablets to slow down thyroid hormone production, surgery to remove the overactive thyroid gland or radiotherapy. If your kitty is suffering from hyperthyroidism your vet will discuss the various options. I suggest you make an appointment tomorrow.

It's wonderful for you to look out for a stray in your neighborhood! While it's impossible to know what he may have gotten into, overly pink skin with missing fur could be a result of a burn - either thermal or chemical. If it's possible to do so, try catching or trapping him to have the lesions examined. Skin can develop infection at the site of a burn wound. That said, we can't rule out other infectious causes of the hair loss, such as ringworm or mange from mites. If you are able to catch or trap him, consider having him neutered (if he isn't already) and vaccinated. Neutering is likely to decrease his aggression towards other cats in the neighborhood. Many shelters and rescues offer spay/neuter clinics for stray animals. I hope this helps!

I would talk to your vet about checking her thyroid hormones. It is probably unlikely but definitely possible that her thyroid is too high causing weight loss and hair loss. I would also make sure she is on a high quality dry and canned cat food to help increase the caloric intake. If you aren't planning on breeding her, I would consider getting her spayed as long as she is healthy enough per your vet. I would definitely continue the vitamins. Also, I would talk to your vet about ruling other things out if they haven't already like parasites, giardia, feline leukemia, feline aids, and more. I hope this helps!