Alopecia by Infection / Disease


Hair loss associated with endocrine diseases, or skin diseases, as in bacterial, parasitic, allergies, pain, and neoplasms.

Clinical Signs

May see any of the following:

  • Localized, or multifocal hair loss.
  • Inflammation, irritation, or scabs associated with scratching.
  • Evidence of parasite, or skin growths at the site of hair loss.

*Note: Thinning hair or hair loss to the back is most often associated with parasites, while thinning hair or hair loss to hindquarters/flank is most often associated with endocrine imbalance.


Hair loss as a result of disease, or infection, can reflect varied patterns. It may be localized, involve more than one area, be symmetrical, or generalized, depending on the underlying causative agent.

Inflammation, itching, lesions or scabs, or neoplastic type growths may be seen; as well as, abrasions from scratching with nails. Secondary infections may be introduced (most often from scratching with nails), such as a bacterial pyoderma from staphylococcus. Seborrhea, or eczema may also be present.

Infections that contribute to this type of acquired alopecia (hair loss) are ectoparasites such as mites, lice, and fleas, or attributed to yeast or fungal infections. Other causes are allergies due to type of diet, especially those high in protein content or lacking in essential fatty acids, and allergic contact dermatitis as with some types of litter used.

In some of the endocrine diseases where there is hair loss, or hair loss attributed to pain, or aging, itching or inflammation is not generally present.

The most often seen acquired infectious/disease associated alopecia in rats is due to infestation of ectoparasites.


Obtain history to determine, if possible, diet allergy, contact allergy or pain. Endocrine disease is suspect if hair loss is known to have occurred in litter mates not housed together.

Skin scraping for ectoparasites.

Serum chemistry, complete blood count, urinalysis if possible endocrine diseases suspect.

Skin cultures for fungal, bacterial or yeast infections.


For parasites, See Ectoparasites.

For possible diet related allergies, see Food Allergies.

For possible allergic contact dermatitis, see Dermatitis

For hair loss related to possible bacterial or fungal infections, see topics under Integumentary/Skin listed in the Rat Health Guide Index page.

Nursing Care

  • Clip nails on a regular basis making sure not to cut the quick. Keep styptic on hand if bleeding occurs.
  • Be consistent when doing soaks, applying ointments, or giving medications.
  • Continue treatment until resolved or until alternative treatment started.
  • Keep cage environment clean and sanitized along with bedding and toys.
  • Maintain an even temperature in the environment that is not too arid or too humid.
  • If diet is the culprit eliminate offending foods.
  • If litter is the culprit change to a different litter or freeze litter to aid in killing parasites, prior to using.


  • Remains free from inflammation or irritation to skin.
  • Underlying cause determined and treated effectively.


  • Quarantine all new rats for a minimum of three weeks and treat for infections if present prior to introducing to existing colony.
  • Maintain a healthy diet.
  • Do not use Cedar or Pine litter. Use reduced or dust free litter.
  • Use of prepackaged processed litter, and the freezing of litter where bags have been breached prior to purchase, may be of help.
    *Please note: that any bags of litter/bedding that have been noted to have a row of holes in the top of the bag or any bag that has been breached during storage in pet stores and feed/tack warehouses, where contamination through contact from residing infested animals, may be a potential risk. Freezing the litter before using in cages may be a helpful preventative measure.
  • Heat and air-conditioning can be drying to the skin. Try to maintain an even temperature in the environment and check skin on a frequent basis for signs of dry flaking dandruff.


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