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Dog’s Anus is Red or Inflamed: Our Vet Shares What to Do

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dog getting a rectal exam by a vet

This article was updated on August 26th, 2023

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It may be alarming if you notice that your dog’s rear end is red, sore, swollen or irritated. A dog with a red inflamed anus will be uncomfortable and more likely to lick, chew, or scoot. For this reason, owners should be aware of the causes of this condition and when to take action if their dog is experiencing signs of pain or discomfort. In this article, we will review the top reasons, when you should worry, and what you may be able to do at home to help your dog while you wait for your vet appointment.

Top reasons causing a dog’s anus to become red or inflamed

Anal irritation or inflammation in dogs is not an uncommon problem. Below we will discuss the likely causes of these clinical signs, and what to do:

1. Diarrhea

Diarrhea is the most common cause of anal discomfort in dogs. Diarrhea often causes increased urgency to go to the bathroom and straining to defecate. This straining can cause worsening inflammation and discomfort of the colon and anus. Dogs with diarrhea may have fecal staining of their perineal region. The diarrhea is caustic due to the presence of gastric acids, digestive enzymes, and bile. This leads to inflammation and ulceration of the perineal skin (redness and irritation of the anus).

Diarrhea can occur for a variety of reasons, including dietary indiscretion, food intolerance, chronic gastrointestinal disease, parasitism, pancreatitis, stress, antibiotic use, and other illnesses. To learn more, read our article: Stop Dog Diarrhea Fast with These Home Remedies.

2. Anal gland disease

Signs of anal gland disease may include excessive scooting, licking, or pain during defecation. 

Dogs have two anal glands situated on either side of their anus. These glands help with the lubrication of feces as well as scent marking during defecation. For a variety of reasons, these glands can become impacted or infected (see this picture on Infected anal glands will irritate the anus and cause local swelling and redness. Rupture of the anal gland can occur, leading to a wound beside the anus and purulent discharge.

3. Perineal cancers

Just like humans, dogs can be predisposed to a variety of cancers. Anal gland adenocarcinoma is a cancerous process arising from the anal glands. It is relatively uncommon but is an aggressive cancer that can invade local tissues and metastasize. These tumors often appear as lumps next to the anus. Dogs with anal tumors may have difficulty defecating. You can click here to see a picture of an anal gland tumor or see another example here on

4. Allergies 

A hallmark sign of flea allergy dermatitis is itching and hair loss of the hind end, especially at the base of the tail. Chronic allergies can lead to itching and hair loss around the perineal region. Dogs can be predisposed to allergies, whether it be to the environment, food, or parasites on the skin. These allergies can lead to itchiness, red skin, and discomfort. Learn about skin allergies & rashes in dogs.

5. Rectal Prolapse

Dogs with chronic diarrhea, cancers, or parasites may be predisposed to rectal prolapse. A rectal prolapse is when the inner surface of the rectum protrudes beyond the anus. The prolapsed tissue will appear bright red and may look similar to a swollen tube. The prolapse may be intermittent and occur during a bowel movement. Sustained prolapses are an emergency as the tissue of the rectum can become devitalized and die, causing the need for emergency surgery. See this example picture from PetCoach.

6. Perineal Fistulas 

Perineal fistulas are caused by an auto-immune condition that leads to severe inflammation and ulceration of the perineal region. Dogs with this condition will develop tracts alongside the anus, which will often have foul-smelling discharge and can lead to bleeding, straining to defecate, and significant pain. German Shepherds are predisposed to this condition. See the example picture (warning: graphic image) from

Can I just monitor my dog and wait?

Mild cases of rectal inflammation and irritation rarely require urgent veterinary intervention. Keeping the dog’s perineal region clean and free of fecal material will help prevent ulceration or worsening irritation. Often, this inflammation may improve with little to no intervention.

Dogs with signs of ongoing diarrhea, pain, bleeding when defecating, or black/tarry stools require urgent veterinary intervention. Waiting may lead to increased discomfort, pain, or constipation secondary to reluctance to defecate. 

What’s an example of mild anal inflammation?

Here is a photo of mild anal inflammation in a dog. A wait-and-see approach for this severity of illness is appropriate. Owners may consider home remedies, including a bland diet and topical treatments. 

When should I be concerned about my dog’s red bottom?

Inflammation and redness around the anus area are always concerning to pet owners but are not always an emergency. The following clinical signs indicate that urgent or emergent intervention is required:

  • Defecating large amounts of blood – A very small amount of blood in the stool can be seen with mild inflammation of the colon and is not overly concerning (view these remedies). A larger amount of blood in your dog’s poop is a sign of significant inflammation of the colon or damage to the local blood vessels. A veterinarian should always address this.
  • Rectal prolapse – This condition is always a medical emergency, especially if the rectum does not return to normal. Delay in medical intervention can lead to necrosis of the rectum causing a need for emergency surgery to rectify the problem.
  • Pain – Any dog that is showing signs of pain or discomfort should be evaluated by a veterinarian as soon as possible. Pain may cause a reluctance to defecate, leading to constipation if untreated.
  • Masses – If you are concerned that your dog has a mass near the anus, a veterinary visit is recommended sooner rather than later. Early diagnosis and intervention of perineal masses may lead to quicker treatment and an overall better prognosis. 
  • Perineal fistulas – If you are concerned that your dog has a perineal fistula, urgent intervention is recommended. Catching the disease in its early phases will allow quicker diagnosis and treatment. This may halt the disease in the early phases leading to quicker relief for your pet and potentially a better response to therapy. 

5 steps you can take at home to help your dog with a red or inflamed anus

First, it is important to recognize that you should not delay veterinary care: a call to your veterinarian is in order to discuss your dog’s particular situation. Below are a few simple tips that may help soothe a dog’s red or irritated anus while you wait for your vet appointment:

  1. Keep your dog’s hind end clean – By removing any residual fecal material, you can prevent ulceration caused by caustic diarrhea. This can be as simple as wiping your dog’s butt clean after a bowel movement. In cases of more severe diarrhea, bathing the area is recommended to remove poo stuck to the fur and also to soothe the region.
  2. Soothing sore skin – Over-the-counter topical treatments can be used to calm irritated or ulcerated skin. Ideal products that are safe to use include Vaseline and Aquaphor. These ointments help heal inflamed skin and also create a barrier to prevent further irritation. These can be applied as needed or after cleaning the perineal region. Do not allow your dog to lick the area after ointment has been applied.
  3. Troubleshooting diarrhea – Dogs with simple diarrhea may benefit from solutions at home. The easiest and move effective treatment an owner can provide is changing their dog’s meals to a bland diet. This diet typically consists of boiled chicken or lean ground beef mixed with white rice. An easily digestible diet may improve most cases of simple diarrhea after a day or two. Learn more: Dog Has Diarrhea for 2 or 3 Days: Is It Serious?.
  4. E-collar to prevent licking – Dogs with anal irritation will feel the need to lick and chew the perineal region. These behaviors will only lead to worsening discomfort and inflammation. An Elizabethan collar is an excellent solution to prevent your dog from further traumatizing its anus. 
  5. Preventative measures – The best way to prevent anal irritation is to try to prevent diseases that cause it in the first place. This means avoiding food items that can cause upset stomachs leading to diarrhea. Monthly flea and tick preventatives will decrease the likelihood of your dog developing flea allergy dermatitis or diarrhea from gastrointestinal parasites. 

How to prepare for your veterinarian visit

Before your veterinary visit, make sure you have any information handy that your veterinarian may need. This includes a timeline and details of the clinical signs as they appeared. Photos of the perineal region or feces may be helpful for the doctor to have a better sense of what is going on. Bringing a fresh fecal sample will facilitate testing for parasites or bacterial overgrowth. 

What would happen at the vet?

At the veterinary office, a series of steps will take place to determine the cause of your dog’s irritated or swollen anus. First, your veterinarian will take a thorough history to help decipher what the underlying cause may be. After they have an understanding of what has been going on, a physical examination will be performed. Part of this physical examination will include a rectal exam. This exam is used to determine if there are any abnormalities of the anus, anal glands, or stool. Your veterinarian may request a fecal sample to evaluate for gastrointestinal parasites or overgrowth of bacteria. If the anal glands are swollen, expression may be performed to alleviate discomfort. In the event of an anal gland impaction or abscess, your dog may need to be sedated to have the anal gland drained. If there is a concern for an anal gland mass, fine needle aspirates are recommended to evaluate if cancerous cells are present. 

Disclaimer: This content is not a substitute for veterinary care. Always consult with your vet for health decisions. Learn more.

Once a definitive diagnosis is made regarding the cause of your dog’s anal irritation, a targeted treatment plan will be discussed. This may include medication or probiotics to improve diarrhea, pain medication, treatment of allergies, or deworming agents to eliminate gastrointestinal parasites. Dogs will perineal masses should have them surgically removed once staging has been performed. Dogs with perineal fistulas or allergies may require treatments with immunosuppressive agents. 


Why is my dog’s anus red & swollen?

Perineal inflammation can be caused by a variety of diseases, including diarrhea, anal gland problems, perineal fistulas, rectal prolapse, and allergic skin disease.

WATCH: 3 Important Tips To Care For an Old Dog [VET VIDEO]

Why is my dog’s anus only red after pooping?

A red anus after defecation may be normal in some dogs as their rectal mucosa can protrude slightly after a bowel movement. Straining to defecate, diarrhea, and constipation can also cause a red anus after defecating. 

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  • Dr Paula Simons, Emergency Vet

    Dr. Paula Simons is an emergency veterinarian at Cornell University Veterinary Specialists (CUVS), a leading 24/7 Emergency and Critical Care Hospital (CUVS is affiliated with the renowned Cornell University College of Veterinary Medicine, a world leader in veterinary care). She graduated with a Doctorate in Veterinary Medicine (DVM) from the Ontario Veterinary College in 2019.

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