TL;DR: While "sleep dust" is typically a normal byproduct of a cat's eye-cleaning process, you should consult a vet if the discharge becomes thick, changes color, or is accompanied by squinting.
What is "sleep dust" in cats and is it normal?
Much like humans, cats can wake up with small amounts of dried discharge in the inner corners of their eyes. This material, often referred to as "sleep dust" or eye crusties, is typically a mixture of dried tears, natural oils, and dust particles. In healthy cats, this discharge is usually clear or turns a brownish-rust color when it dries due to a pigment called porphyrin. It is a normal part of the body's self-cleaning mechanism for the ocular surface.
When is my cat's eye discharge considered a medical emergency?
- The urgency level for simple, occasional eye crusties is Low if your cat is behaving normally, eating well, and the eye itself appears clear and white.
- Contact your veterinarian for a routine check-up if you notice a sudden change in the amount of discharge.
- Seek veterinary care if the discharge becomes thick, yellow, or green to rule out a respiratory infection or conjunctivitis.
Why should I take a photo of my cat's eyes to help with triage?
- Provides a vital baseline for your veterinary team to track swelling, redness, or the specific appearance of discharge.
- Helps a professional determine if the issue is a simple case of "sleep dust" or requires a physical examination.
- Captures clinical signs of irritation, such as squinting or cloudiness, which can change rapidly before an appointment.
Clinical Context (Merck Veterinary Manual)
In cats, mild ocular discharge can be associated with conjunctivitis caused by bacteria, viruses, mycoplasma, fungi, parasites, or environmental irritants. Common infectious agents like feline herpesvirus 1, Chlamydia, and Mycoplasma frequently manifest as acute or recurrent conjunctivitis. Diagnosis involves history, physical examination, conjunctival scrapings and culture, and Schirmer tear test. While unilateral conjunctivitis may result from a foreign body, dacryocystitis, or keratoconjunctivitis sicca, feline herpesvirus 1, Mycoplasma, or Chlamydia psittaci may produce conjunctivitis that begins in one eye and becomes bilateral after approximately one week.
Chapter: Infectious Disease, Ophthalmology
Source: The Merck Veterinary Manual, 11th Edition (Page 1482)