Cat Hair Loss Without Fleas or Rash: Differential Diagnosis

Feline alopecia without obvious pruritus or fleas requires systematic evaluation.

Common Non-Pruritic Causes

1. Psychogenic alopecia (overgrooming): Stress-induced; symmetric, ventral abdomen, medial thighs, perineum. Diagnosis of exclusion.
2. Endocrine:
   • Hyperthyroidism (common >10 yr): weight loss, polyphagia, vomiting, unkempt coat.
   • Hypothyroidism (rare, usually iatrogenic): lethargy, weight gain, symmetric truncal alopecia.
   • Cushing's (hyperadrenocorticism): rare; thin skin, comedones, polyuria/polydipsia.
3. Nutritional: Protein/essential fatty acid deficiency (poor diet, malabsorption).
4. Neoplastic: Paraneoplastic alopecia (thymoma, pancreatic carcinoma)—rare, severe.
5. Congenital/genetic: Colour dilution alopecia, follicular dysplasia (breed-specific).
6. Drug reaction: Topical/oral medications.
7. Normal aging: Thinning, not patchy loss.

Pruritic Causes (Subtle Itch)

• Atopic dermatitis (feline atopy)
• Food allergy
• Mites (Demodex, Notoedres, Cheyletiella)—skin scrapings
• Fungal (dermatophytosis/ringworm)—Wood's lamp, culture

Diagnostic Workup

• History: onset, progression, environment, diet, stressors, meds.
• Physical: distribution, skin quality, claws, lymph nodes.
• Combings, scrapings, tape prep, fungal culture.
• CBC, chemistry, T₄, urinalysis.
• Skin biopsy if non-diagnostic.

Management

Treat underlying cause. Psychogenic: environmental enrichment, pheromones (Feliway), anxiolytics (fluoxetine, clomipramine). Endocrine: specific therapy. Nutritional: balanced diet + supplements.

Veterinary consultation is essential—self-diagnosis delays effective treatment.