Petco Text Logo
Petco Pet Logo

My cat is still scratching after 6 weeks on new food. Is it allergies?

Updated On September 23rd, 2025

Pet's info: Cat | Domestic Shorthair | Female | spayed | 1 year and 2 months old | 8.2 lbs

The vet and I have been wanting to see if Luna is allergic to her food, so she's been on this food for more than 6 weeks now (and she eats nothing else). Shouldn't she have stopped scratching by now if she's really allergic to normal food? Or how long should I wait to see if the food is working and it was her other regular food that was making her itchy?

This question includes photos that may contain sensitive content. Click to view.

View more to consider that the photos may include sensitive content.

2 Answers

Most Helpful Answer

Image profile

Answered By Dr. Massimo Orioles, DVM, Cert AVP, MRCVS

Veterinarian

Published on May 21st, 2018

I would recommend to wait up to 8 weeks before thinking about other causes. If not working, a skin scrape and more dermatological tests (including allergic testing on bloods) are required to determine if other causes are possible. Three main type of allergies are usually affecting pets: food allergies, flea and parasite related ones and environmental type (allergens coming from trees, pollens, dust etc etc). Some medications can be given by the vet in order to repair any possible skin lesions (like steroids and antibiotics). Hope this answer was helpful, but please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.

Vote icon

1Pet Parents found this answer helpful

Related Answers from Veterinarians

  • Image profile

    Answered By Jenna Beyer, DVM, MBA, cVMA

    Veterinarian, Certified Veterinary Acupuncturist

    Published on October 15th, 2017

    I would recommend a checkup with your vet. Benadryl doesn't work for every pet, and it sounds like it is not working at all for Midnight. There are other antihistamines that can be used, but you will have to discuss them with your regular vet since it is illegal for us to prescribe them without examining her. There are also other causes for allergies if not from fleas, such as from the environment or to food. You may try a food trial to see if you can find something that Midnight is allergic to. This is the list of most common food allergens in dogs, but it is similar to cats: Beef – 32% Chicken -26% Lamb - 20% Pork - 16% Dairy - 14% Less than 1% of dogs diagnosed with food allergies will be allergic to grains Here is a great article on food trials and how to do them: http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=2499

    Vote icon

    1Pet Parents found this answer helpful

See More Answers

Related Questions

Petco Pet Education Center
New Pet
What’s wrong with my kitty? He’s a year and 8 months old :(
This is probably due to an allergy, although it could also be infection or mites. First of all, in order to rule out skin parasites, you will need to treat with a high quality flea treatment, then ask the vet to perform a skin scrape - this might reveal an infection or a mite infestation. If all of those came back negative, the next step is to treat the allergy symptomatically and try to discover the cause of the allergy. Three main type of allergies are usually affecting pets: food allergies, flea and parasite related ones and environmental type (allergens coming from trees, pollens, dust etc etc). Some medications can be given by the vet in order to repair any possible skin lesions (like steroids and antibiotics). Hope this answer was helpful, but please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.
Updated on September 24th, 2025
Petco Pet Education Center
Health & Wellbeing
My Jack Russell started scratching and nibbling his back causing red skin about a month ago then I noticed I had switched his food so I'm thinking he is having a food allergy so I switched back to his regular food about 2 weeks ago and their is a lit
First you have to rule out other things as well like fleas and secondary infection which can both be itchy. If there are any lesions under the skin there may be a secondary infection (common with allergy). For food allergy it can take time for symptoms to resolve (8+ weeks for some dogs) and those pets who are very itchy may need medications to stop the itch (itching can lead to secondary skin infection as well). So if your pup is very itchy you may want to talk to your family vet about meds to help with itch while going back to the old food. And treat for fleas just in case (even if you do not see any). I hope this helps and thank you for using Boop by Petco!
Updated on September 24th, 2025
Petco Pet Education Center
Health & Wellbeing
Mellie has been scratching the area above her hips close to the abdomen for several months. She has no hair on the right side. The patch is 3" x 3" approx. Her food has not changed since the day we got her. She does not have any "bugs". We went to th
This is probably due to a severe allergy, although it could also be fleas, infection or mites. First of all, in order to rule out skin parasites, you will need to treat with a high quality flea treatment (advocate or advantage), then ask the vet to perform a skin scrape - this might reveal an infection or a mite infestation. If all of those came back negative, the next step is to treat the allergy symptomatically and try to discover the cause of the allergy. Three main type of allergies are usually affecting pets: food allergies, flea and parasite related ones and environmental type (allergens coming from trees, pollens, dust etc etc). Some medications can be given by the vet in order to repair the skin lesions (steroids and antibiotics). Please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.
Updated on September 24th, 2025
Petco Pet Education Center
Health & Wellbeing
My cat developed these skin allergy? on her face since two months.
This is probably due to an allergy, although it could also be infection or mites. First of all, in order to rule out skin parasites, you will need to treat with a high quality flea treatment, then ask the vet to perform a skin scrape - this might reveal an infection or a mite infestation. If all of those came back negative, the next step is to treat the allergy symptomatically and try to discover the cause of the allergy. Three main type of allergies are usually affecting pets: food allergies, flea and parasite related ones and environmental type (allergens coming from trees, pollens, dust etc etc). Some medications can be given by the vet in order to repair any possible skin lesions (like steroids and antibiotics). Hope this answer was helpful, but please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.
Updated on September 24th, 2025
Petco Pet Education Center
Health & Wellbeing
Hi there! I have adopted a cat around three months ago. About a month ago he started scratching his ears, neck, and chin. He’s a black kitty who fur too dense to see skin. I’ve been feeding him the same kind of food since adopting him so I don’t thin
Hi, and thanks for your question. This could be due to an allergy, although it could also be infection or mites. First of all, in order to rule out skin parasites, you will need to treat with a high quality flea treatment, then ask the vet to perform a skin scrape - this might reveal an infection or a mite infestation. If all of those came back negative, the next step is to treat the allergy symptomatically and try to discover the cause of the allergy. Three main type of allergies are usually affecting pets: food allergies (they can unfortunately manifest even if you do not change the food as they may take a while to build up), flea and parasite related ones and environmental type (allergens coming from trees, pollens, dust etc etc). Some medications can be given by the vet in order to repair any possible skin lesions (like steroids and antibiotics). Hope this answer was helpful, but please do not hesitate to contact us again on the forum or by requesting a consultation if you have an
Updated on September 24th, 2025
Petco Pet Education Center
Health & Wellbeing
My rescuer keeps scratching and we bought flea and tick medication you put down the middle of her back. But it seems like it's getting worse. She's also timid and hard to walk , any suggestions
This is probably due to an allergy, although it could also be infection or mites. First of all, in order to rule out skin parasites, you will need to treat with a high quality flea treatment, then ask the vet to perform a skin scrape - this might reveal an infection or a mite infestation. If all of those came back negative, the next step is to treat the allergy symptomatically and try to discover the cause of the allergy. Three main type of allergies are usually affecting pets: food allergies, flea and parasite related ones and environmental type (allergens coming from trees, pollens, dust etc etc). Some medications can be given by the vet in order to repair any possible skin lesions (like steroids and antibiotics). Hope this answer was helpful, but please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.
Updated on September 24th, 2025
Petco Pet Education Center
Health & Wellbeing
My persian cat have an allergy. He scraths and lick and lost almost all his hair. I think may may its the food. He do not have fleasf He is an indoor cat He is is 3march one year old. IIgiveI him royal canin exigent mix with hair and skin food.
Thanks for using Boop by Petco! This is possibly due to allergies. It really comes down to figuring out what is causing his allergies so that they can be treated or the specific allergen avoided. There are many things that can cause allergies though in most cases they can be broken down into 3 big categories: flea, food and environmental allergies. Allergies are usually worked up in a stepwise fashion starting with flea allergies as this is the easiest and cheapest to take care of. If not on a flea preventative, then it would be a good idea to get started on one. If already on one then it would be a good idea to change to something else (there are many new products out in the market). If not improved in 1-3 months then it is time to move on and check for food allergies by switching to a novel diet (new protein and new carbohydrate). If that does not seem to be the issue then you are left out having to check for environmental allergies which require blood and/or skin tests. Aller
Updated on September 24th, 2025
Petco Pet Education Center
Health & Wellbeing
I have a blond Mini Daschund 8 yrs old. She is always scratching herself. We have her on Hills Science Diet Small Breed Weight Control Small Bites. She has no fleas or parasites. Could it be her food and what kind would you suggest. When she scratche
Thanks for using Boop by Petco! This is possibly due to allergies. It really comes down to figuring out what is causing her allergies so that they can be treated or the specific allergen avoided. A secondary infection is likely and also needs to be addressed. There are many things that can cause allergies though in most cases they can be broken down into 3 big categories: flea, food and environmental allergies. Allergies are usually worked up in a stepwise fashion starting with flea allergies as this is the easiest and cheapest to take care of. If not on a flea preventative, then it would be a good idea to get started on one. If already on one then it would be a good idea to change to something else (there are many new products out in the market). The Royal canin ultamino is great for food allergies. If not improved in 1-3 months then it is time to move on and check for food allergies by switching to a novel diet (new protein and new carbohydrate). If that does not seem to be the
Updated on September 24th, 2025
Petco Pet Education Center
Health & Wellbeing
Our persian cats 8 years old 7,3kg. Have a redness on his back and had.And he is itchin to much almos 1.5 month.Vet said he have a allergy(we stop giving him besides his food) once he shaved after that he blooded his back with itching his self.Vet hi
I'm sorry to hear that Gofret is having so much trouble! There are a number of things that can cause itching similar to what you describe - it's true that allergies are one of the most common causes, but he could also have a bacterial or fungal skin infection, parasites like fleas, or even skin mites (mange). Your vet should test for these things if this hasn't been done already. If skin tests for all of these problems are negative, then it's likely that your cat has an environmental allergy of some kind since the hypoallergenic diet has not helped. In that case, you will probably need to use a long-term medication to control his symptoms such as prednisone, Atopica, or Apoquel. It may also be an option to have allergy testing done so that you can do hyposensitization injections if you wish - you can ask your vet for referral to a veterinary dermatologist, or get a second opinion from another veterinarian in the area if needed.
Updated on September 24th, 2025
Petco Pet Education Center
Health & Wellbeing
My dog has really bad allergies. We went to the vet & decided to do trials with food to see what helps. I bought him a new dog food & about a week later you could tell he was worse, he was itching more, ear infections, rashes, he was allergic to this
It can sometimes take up to two months to fully see results of a new food before any symptoms are completely gone if it is a food-based reaction. I would hesitate to keep switching foods as you won't be able to accurately judge if a food is causing it and may just cause added GI upset on top of the itching and scratching. If Jax is still breaking out very badly it would be best to contact the vet doing the food trial with you so they can take note and make suggestions on whether a change should happen or if you should stay on the food for a while longer.
Updated on September 24th, 2025
image
Have A Vet Question?

Book an appointment with the pros – our expert vets are here to help.

Book Now

Sponsored