Guinea pig conjunctivitis — pink, swollen, weepy eyes — is usually a sign of one of three underlying causes: Bordetella or Streptococcus respiratory infection extending to the eye, a hay or bedding foreign body lodged behind the eyelid, or vitamin C deficiency damaging the conjunctival blood vessels. A truly isolated eye problem in a guinea pig is uncommon (Pignon & Mayer, 2011, Vet Clinics NA Exotic). Treatment starts with finding the actual cause, not just an eye drop.
Last reviewed: June 2026
What Guinea Pig Conjunctivitis Looks Like at Home
The clearest signs are redness of the white of the eye (sclera) and the inner lining of the eyelid, swelling of the lids, watery or pus-like discharge, squinting, and matted or stained fur around the eye. Some guinea pigs paw at the face or rub against bedding. Discharge can be clear (more typical of irritation or early infection) or yellow-green and crusty (suggesting bacterial infection). One eye versus both eyes matters: unilateral disease often points toward foreign body or trauma; bilateral disease more often points toward respiratory infection or vitamin C deficiency.
Cause 1: Respiratory Infection Extending to the Eye
Guinea pigs are particularly vulnerable to bacterial respiratory infections caused by Bordetella bronchiseptica and Streptococcus pneumoniae. Both pathogens can extend up the nasolacrimal duct and produce conjunctivitis as part of a broader respiratory illness. The 2011 review of exotic small mammal infectious disease reported that 20 to 40 percent of guinea pigs with overt respiratory disease have ocular signs (Pignon & Mayer, 2011, Vet Clinics NA Exotic). The clue is concurrent sneezing, nasal discharge, reduced appetite, or audible respiratory noise. A guinea pig with both eyes weeping AND clear nasal discharge needs an exotic vet promptly because Bordetella pneumonia is the leading cause of respiratory mortality in this species.
Cause 2: Hay or Bedding Foreign Body
A unilateral red, painful, weepy eye in an otherwise normal-acting guinea pig is most often a hay or bedding particle lodged behind one of the eyelids. Timothy and orchard hay stems are stiff and easily catch the conjunctival sac. The guinea pig squints, tears, and may have a corneal scratch. Diagnosis is via fluorescein staining (to look for a corneal ulcer) and careful eyelid eversion under sedation if a foreign body is suspected. As described in Quesenberry and Carpenter's Ferrets, Rabbits, and Rodents, hay foreign bodies are one of the most common eye problems in pet guinea pigs and respond rapidly to removal plus a short course of topical antibiotic.
Cause 3: Vitamin C Deficiency (Scurvy)
Guinea pigs, like primates, cannot synthesize vitamin C and must consume it daily. Deficiency develops within 2 to 4 weeks of inadequate intake and produces a recognizable syndrome: weakness, lameness, swollen joints, fragile bleeding gums, poor coat, slow wound healing, and ocular signs including conjunctival hemorrhage and discharge. The 2024 AEMV exotic mammal care library highlights vitamin C as among the most common pet guinea pig husbandry failures (AEMV Pet Care Guides, 2024). Daily vitamin C requirement is roughly 10 to 30 mg per kilogram. Stale or improperly stored pellets lose vitamin C content rapidly. Adding fresh red bell pepper, parsley, or kale daily, plus a quarter of a 100-mg vitamin C tablet, prevents deficiency reliably.
Less Common but Important Causes
Dental disease — overgrown molars can compress the tear duct and produce ocular discharge. Trauma — bites from cage mates, scratches from rough handling. Pea eye — a benign herniation of conjunctival tissue, more cosmetic than dangerous, more common in older guinea pigs. Chlamydophila caviae — a specific eye-targeting bacterial pathogen, particularly in young guinea pigs from breeders.
What the Vet Workup Looks Like
A good guinea pig conjunctivitis workup includes a thorough head and respiratory exam, fluorescein staining of the cornea to rule out an ulcer, eyelid eversion to look for foreign bodies, ear and nasal evaluation, and a brief dental exam under sedation if dental disease is suspected. Cytology or culture of the discharge guides antibiotic selection. Skull radiographs are added when dental disease is on the list. Treatment depends on cause: topical antibiotic and lubricant for foreign-body and superficial infection; systemic antibiotics for respiratory disease (commonly trimethoprim-sulfa, sometimes azithromycin); dietary vitamin C correction for scurvy; and dental treatment if indicated.
When to See a Vet
Call your vet today if:
- One or both eyes are red, swollen, or weepy
- Squinting, pawing at the eye, or matted fur around the eye
- Concurrent sneezing, nasal discharge, or audible breathing sounds
- A guinea pig with poor coat, weakness, or wobbly gait (possible scurvy)
- A new piggy from a breeder or store with weepy eyes (possible chlamydia)
Go to the ER immediately if:
- Your guinea pig is not eating or producing droppings (GI stasis is an emergency in this species too)
- Severe respiratory distress (open-mouth breathing, blue gums)
- Bleeding gums or bleeding into the eye
- Sudden inability to walk or significant weakness
- Profound lethargy with hunched posture
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Frequently Asked Questions
What is the most common cause of guinea pig conjunctivitis?
In pet guinea pigs, the top three causes are bacterial respiratory infection extending to the eye, hay or bedding foreign body, and vitamin C deficiency. Less common causes include dental disease, trauma, pea eye, and Chlamydophila. A bilateral weepy eye with sneezing leans respiratory; a unilateral red eye in an otherwise normal pig leans foreign body; eye changes with weakness or wobbly gait lean scurvy.
How much does guinea pig eye treatment cost?
Initial exotic vet exam runs $75 to $200 in the US. Fluorescein staining and eyelid eversion add $30 to $80. A topical antibiotic course is typically $30 to $80. Systemic antibiotics for respiratory disease run $50 to $150. Chest radiographs are $200 to $400. Sedated foreign-body removal is $200 to $500. Daily vitamin C supplementation is under $10 per month and prevents many of these problems entirely.
Can a guinea pig eye infection go away on its own?
A mild case of irritation from temporary dust exposure may resolve, but established conjunctivitis — particularly with discharge or visible swelling — does not reliably self-resolve and risks corneal ulceration if untreated. A vet visit within 24 to 48 hours is appropriate.
How much vitamin C does my guinea pig need daily?
Approximately 10 to 30 mg per kilogram body weight per day for adults; pregnant or sick pigs need closer to 30 mg per kilogram. A guinea pig in good health gets this from fresh red bell pepper, leafy greens (kale, parsley, cilantro), and a small portion of vitamin-C-fortified pellets eaten within the first 90 days of bag opening. A quarter of a 100-mg human vitamin C tablet daily is a reliable safety net.
Is guinea pig conjunctivitis contagious?
Bacterial respiratory infections like Bordetella and Streptococcus are contagious to other guinea pigs and should prompt isolation and treatment of all in-contact pigs. Chlamydophila caviae is contagious between guinea pigs. Foreign-body conjunctivitis and scurvy-related eye disease are not contagious. Treating all in-contact pigs for respiratory disease often makes sense even before culture results return.
Still Not Sure if Your Guinea Pig Needs a Vet?
When you're not sure if this is wait-and-see or call-tonight, Voyage AI Vet triages in under 2 minutes. Describe what you're seeing in chat, share photos of the eye in good light (close-up if possible) and any nasal discharge or droppings, or hop on a live video call if you want a second pair of eyes. Every answer comes with citations to the actual veterinary literature it's pulling from — so you see exactly where the guidance comes from, not just a chatbot's word.