Seborrhea

• Epidermal growth or differentiation disorder

Seborrheic disease complex

• Abnormal cornification or function of sebaceous glands
• Large amounts of free fatty acids and cholesterol
• Decreased amounts of diester waxes in surface lipids
• Bacterial population changes to pathogenic coagulase positive staphylococci
• Chronic disease affecting mainly dogs, sometimes cats and horses
• Dry form - white to grey scales
• Greasy form - scaly, excess brown to yellow lipids sticking to skin and hair

Primary idiopathic seborrhea

• Abnormal cornification
• Epidermal turnover reduced to about 2/3 of normal
• Microscopically:
  • Hyperkeratosis distending follicular ostia causing papillary appearance
  • Parakeratosis at edges of follicular ostia
  • Congested, oedematous dermal papillae
  • Spongiotic epidermis with leukocytes

Secondary seborrhea

• Develops secondarily to many types of disease (e.g. ectoparasites, fungal infections, endocrine disease, internal disease or allergy)
• Microscopically:
  • Hyperkeratosis and/or parakeratosis of follicles and epidermis
  • Lesions relevant to the other disease