Why did a rat develop a bald spot? - briefly
The most common cause of a hairless area in a rat is a mite‑induced skin disease such as mange, which destroys hair follicles and leads to localized alopecia. Stress, poor nutrition, or hormonal imbalances can also produce hair loss, but parasitic infection is typically the primary factor.
Why did a rat develop a bald spot? - in detail
Rats may lose hair in a localized area for several physiological and pathological reasons.
Genetic factors
- Certain strains carry mutations that affect follicle development, leading to congenital alopecia.
- Autosomal recessive genes can produce a lack of pigment cells, causing hair follicles to abort during embryogenesis.
Hormonal disturbances
- Hyperthyroidism accelerates metabolism, disrupting the hair growth cycle and producing thinning patches.
- Elevated glucocorticoids, whether endogenous or administered experimentally, suppress keratinocyte proliferation, resulting in focal hair loss.
Parasitic infestation
- Demodex mites inhabit hair follicles; heavy colonization provokes inflammation and follicular destruction.
- Flea or mite bites trigger pruritus, prompting the animal to scratch vigorously, which can shear hair and damage follicles.
Nutritional deficiencies
- Insufficient protein reduces the availability of amino acids needed for keratin synthesis, weakening hair shafts.
- Deficits in essential fatty acids impair sebaceous gland function, leading to dry skin and brittle hair that breaks off.
Dermatological disease
- Dermatophytosis (ringworm) infects the epidermis, causing circular alopecic lesions that expand as the fungal hyphae invade.
- Autoimmune alopecia, such as alopecia areata, involves lymphocytic attack on hair follicles, producing sharply demarcated bald spots.
Physical trauma
- Repeated pressure from cage bars or bedding can cause localized ischemia, depriving follicles of oxygen and nutrients.
- Surgical incisions or wound healing may result in scar tissue that lacks hair follicles.
Environmental stressors
- Chronic exposure to low humidity or extreme temperatures can dry the skin, making hair more prone to loss.
- Overcrowding and social hierarchy disputes increase cortisol levels, which indirectly affect hair growth cycles.
Each of these mechanisms operates through disruption of the anagen (growth) phase, premature entry into catagen (regression), or direct follicular destruction. Identifying the specific cause requires clinical examination, laboratory testing for parasites and pathogens, hormonal assays, and assessment of diet and housing conditions.