SYMPTOM
Excessive licking of hindquarters
A dog turns repeatedly to lick, nibble or bite under the tail, around the anus, at the vulva or sheath, or over the tail base and the backs of the thighs, for longer or more often than normal grooming. It may come with scooting along the ground, straining or pain on passing faeces, discharge, a swelling beside the anus, damp or sore skin, or a penis that stays outside the sheath.
Anal Gland Disease
The paired anal sacs can become impacted, inflamed or infected, and the discomfort prompts a dog to lick or bite at the area or to scoot along the ground. Small breeds are predisposed, overweight dogs tend to have repeated problems because the sacs empty poorly, and diarrhoea or constipation can also lead to anal sac disease. An infected or abscessed sac is severely painful and shows as a red or discoloured swelling beside the anus that can burst through the skin and leave a discharging wound. Whether a sac is simply full or is infected cannot be judged at home from the licking alone.
Skin Irritation & External Parasites
Flea bites, contact irritants or localised allergic dermatitis around the tail base and perineum are itchy and drive focused licking. In flea allergy dermatitis the itch is moderate to severe, and the itching and hair loss are most often seen from the middle of the back to the tail base and down the rear legs. Live fleas are often not seen on an allergic dog unless the infestation is heavy, and a single bite can cause itching for several days. Licking and chewing can lead to acute moist dermatitis (hot spots) and bacterial skin infection.
Urogenital Irritation
Hormone-responsive urinary incontinence most often affects middle-aged to older spayed females, typically as urine leaking during sleep or rest, and the urine can scald the skin around the vulva. Vaginitis occurs as a juvenile form in females under a year old, which often resolves after the first season, and as an adult form that usually affects spayed females. Its signs include vulval discharge, licking and scooting. In a female that is still entire, discharge at the vulva in the weeks after a season can also come from pyometra, a life-threatening infection of the womb, and the two cannot be told apart at home. Vaginal hyperplasia is driven by oestrogen, appears as a mass at the vulva most commonly around proestrus or oestrus, and is seen in dogs that are still entire. In males, phimosis can let urine pool inside the sheath. In paraphimosis the penis cannot return into the sheath: the exposed penis swells rapidly, then becomes dry and painful, and licking makes it worse.
Perianal Fistula (Anal Furunculosis)
Chronic, deep ulceration around the anus causes ongoing discomfort that leads to persistent licking, discharge and a strong odour. German Shepherd Dogs are the breed most commonly affected and the condition is seen most often in middle-aged dogs. The cause is unknown but is suspected to be immune-mediated with a genetic predisposition.
Compulsive or Anxiety-Driven Licking
In some dogs, hindquarter licking becomes a repetitive, self-reinforcing behaviour, following a similar pattern to tail-chasing. Contributing factors include an unpredictable daily routine, too few outlets for normal behaviour and chronic or recurrent anxiety. This explanation is reached only after skin allergy, parasites, infection, nerve disease and pain from any cause have been excluded, which cannot be done from the appearance of the skin at home.
Why timing matters
Early observation
Early recognition lets the cause be identified before licking adds skin damage. Three causes progress quickly. A penis that stays outside the sheath swells rapidly because its blood drainage is compromised, and it is more easily treated before severe swelling and pain develop. An infected anal sac can form an abscess that bursts through the skin. Womb infection (pyometra) in an entire female can make a dog seriously ill very quickly.
Later presentation
With continued licking the skin can develop hot spots and bacterial infection. An exposed penis that is not returned to the sheath becomes dry and painful and can go on to tissue death, which may mean part of the penis has to be removed. Perianal fistulas are chronic, ulcerating tracts.
The licking looks much the same whatever the cause. The site (under the tail, the vulva, the sheath or the skin of the rump), the dog's sex and neuter status, and accompanying signs such as scooting, straining, discharge, swelling or urine leakage point towards the source, and the causes are told apart by examination of the area.
Conditions commonly associated
Urinary Incontinence
Leaking urine can scald the skin around the vulva or sheath, and a dog may lick at the wet or sore area.
Anal Gland Disease
Dogs with anal gland discomfort lick or bite at the area under the tail and scoot along the ground.
Anal Furunculosis (Perianal Fistulas)
Dogs with anal furunculosis lick at the painful, inflamed skin around the anus.
Phimosis and Paraphimosis
A penis trapped outside the sheath swells rapidly and is licked repeatedly, and the licking adds to the damage.
Tail-Chasing in Dogs
Tail-chasing can be a compulsive behaviour, and some affected dogs also lick or chew at the tail and hindquarters.
Vaginal Hyperplasia
The visible mass of swollen vaginal tissue draws repeated attention and licking from the dog.
Vaginitis
The discomfort and discharge that come with vaginitis commonly prompt repeated licking at the vulval area.
Flea Allergy Dermatitis
In dogs, flea allergy causes itching and hair loss most often from the middle of the back to the tail base and down the rear legs, so licking and chewing centre on the hindquarters.
Pyometra
In an entire female, pus from an open pyometra can drain from the vulva onto the skin or hair under the tail, and this may draw licking at the area.
When to explore further
When the penis stays outside the sheath and does not go back in
When there is a painful, red or discoloured swelling beside the anus, or a wound or discharge there
When the licking persists or worsens, or comes with scooting, straining, pain on passing faeces, vulval discharge, a mass at the vulva or urine leakage
Noting when this symptom occurs, any triggers, and how it changes over time can provide useful information for veterinary discussions.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS