We will introduce new information about mouse breeding and health every week to provide education for aspiring mouse care experts. Today we will introduce you to a common skin disease in mice - Ulcerative Dermatitis. 


What is Ulcerative Dermatitis?


Polyfocal Dermatitis

Proportion of disease

Ulcerative dermatitis (UD) is a common idiopathic skin disease in the mouse population. The occurrence rate in C57BL/6 background mice is 1-26%.

Disease-causing site

Classically, lesions are pruritic and are located on the dorsum, in the cervical area, between the scapulae, in the axillary area, or a combination of these. It is relatively rare on the abdomen, feet, or tail. Small shallow lesions may rapidly progress to excoriation, ulceration, and skin degloving. 

Symptoms of ulcerative dermatitis

  • The initial symptoms include skin hair loss, skin ulceration, and flushing spots.

  • Common skin damage, even the skin epidermis has been missing, exposing the subcutaneous tissue.

  • Sometimes accompanied by opportunistic bacterial infections and deep skin ulcers.

  • There is often interstitial fluid outflow, or scabs may form.

  • Rarely, ulcers are seen deep in muscles or bones.


What are the Possible Causes of Ulcerative Dermatitis?

1. First of all, the possibility of pathogenic and parasitic infections should be ruled out:

  • Eczema dermatitis caused by Staphylococcus aureus mainly occurs on the face, ears, neck, shoulders and forelimbs, and can develop into ulcerative dermatitis, abscesses (including staphylococcal granulomas), and cellulitis.

  • B-type hemolytic streptococcus skin infection can cause ulcerative dermatitis of the trunk, which can be manifested as gangrene. Systemic infections can manifest as conjunctivitis, rough hair, shortness of breath, lethargy and weight loss.

  • Severe mite infection can cause severe itching in animals, leading to ulcerative dermatitis on the neck and face.

 2. Ulcerative dermatitis may be spontaneous:

  • Ulcerative dermatitis in mice may be caused by friction or excessive grooming injuries.

  • The cause cannot be found in certain mouse strains, such as B6 ulcerative dermatitis, nor is it a secondary infection of excessive grooming.

  • Studies have shown that ulcerative dermatitis in rats is related to Staphylococcus aureus and self-induced scratches.

3. Environmental factors that may contribute to ulcerative dermatitis (UD):

  • The incidence of ulcerative dermatitis fluctuates seasonally, indicating that environmental factors may play a role.

  • During periods of significant seasonal changes in temperature and humidity, i.e. winter and early spring, the incidence of UD appears to increase.

  • Studies have shown that the incidence is related to dietary fat, and mice with a high fat or casual diet are more susceptible than mice with a fat-restricted diet.


Typical Gross Appearance of Ulcerative Dermatitis in a Mouse



Head & Face






Hind legs






  • Suitable temperature and humidity conditions

  • After finding the abnormality, trimming the toenails of the mouse in time


Treatment Measures

Graded treatment

According to the size of the sore, whether the sore is healed, and the prognosis, it can be divided into mild, moderate, and severe:

  • Mild

Symptoms: The sore surface has been or is about to scab, and the animal is in good condition.

Nursing plan: iodophor smear, most cases can also heal by themselves.

  • Moderate

Symptoms: The animal continues to scratch or there is continuous fluid leakage from the sore surface, the sore surface is more difficult to heal, and the animal's mental state is acceptable.

Nursing plan: Iodophor smear. Observe the recovery of the sore surface, use antibiotics, and trim the toenails.

  • Severe

Symptoms: The sore is large and there is no sign of healing, the animal is depressed, and the prognosis is poor.

Nursing plan: Consider implementing euthanasia.

Other treatment options

  • Antibiotics, corticosteroids, antihistamines, antifungal drugs, antibacterial ointments, supplementary dietary vitamins (VE), etc.

The disadvantage of the above is that the effect is unstable: sometimes effective, sometimes ineffective.