Why does my guinea pig cage smell? How to get rid of the ammonia smell

Guinea pigs themselves don’t smell much. The smell comes from their urine, and from the bedding and hay that hold onto it. So a smelly cage almost always has a fixable cause.

What causes a guinea pig cage to smell?

The main smell is ammonia, which forms when bacteria break down urine in damp bedding. The longer wet bedding sits, the stronger the smell. The most common causes are:

• Soiled bedding left too long. Guinea pigs pee a lot, and they tend to use the same corners.
• Bedding that isn’t absorbent enough, or fleece without an absorbent layer underneath.
• A cage that’s too small. When a pair shares too little floor, every part of it gets used as a toilet.
• Urine scale (a white, chalky crust) on the cage base. It holds onto smell even after you change the bedding.
• Poor airflow, such as a cage in a closed-up room, a cupboard or a corner.
• Hay left under the hay rack, which gets peed on and goes damp.
• Uneaten fresh food that’s starting to spoil.

Is the ammonia smell bad for guinea pigs?

Yes. Ammonia irritates the eyes and airways, and guinea pigs sit at floor level, where the fumes are strongest. If the cage smells strongly to you when you’re standing, it’s worse for them.

Guinea pigs are prone to respiratory infections, so a cage that always smells is a welfare issue, not just a housekeeping one. If your guinea pig is sneezing, has crusty eyes or a runny nose, or is breathing noisily, see a vet experienced with exotic pets.

How to stop a guinea pig cage smelling: 8 fixes

1. Spot-clean every day

It takes 5 to 10 minutes. Remove droppings, wet patches and soiled hay, especially from the pee corners and the “kitchen” area near the hay. This does more to control smell than anything else. See our full cage cleaning routine.

2. Change the bedding fully once a week

Take everything out, wipe the base, let it dry and put in fresh bedding. The pee corners may need changing every day or two.

3. Use absorbent, unscented bedding

Paper bedding and fleece liners with an absorbent layer both control smell well. Avoid pine and cedar shavings and scented bedding. They contain oils or perfumes that can irritate your pigs’ airways. Compare options in our bedding guide.

4. Remove urine scale with vinegar

Wipe the base with a 50:50 mix of white vinegar and water, leave it for a few minutes, scrub, then rinse and dry. Corflute bases in C&C cages clean up especially well.

5. Give them more floor space

More floor means waste is spread out and pigs have clean areas to rest in. A pair needs at least 1 m² of floor. If your cage is well below that, a bigger cage will smell less. See is your guinea pig cage too small?

6. Improve airflow, but avoid draughts

Keep the cage in a well-ventilated room, not in a cupboard or a closed-off corner. Open-topped cages like C&C cages and playpens let ammonia escape better than enclosed hutches. Read where to put a guinea pig cage for more.

7. Put a litter tray or extra bedding in the pee corners

Many guinea pigs pee in the same spots, often under the hay rack or inside hides. A shallow tray of paper bedding with hay on top in those spots makes daily cleaning quicker.

8. Wash fleece properly

Fleece that smells even when it’s clean usually has built-up detergent or fabric softener, or needs washing more often. Shake off hay and poop first, use an unscented detergent, skip the fabric softener and wash every 2 to 3 days.

What not to use

• Air fresheners, plug-ins, candles or essential oils near the cage.
• Scented bedding or deodorising powders sprinkled in the cage.
• Bleach that isn’t fully rinsed off. If you use a disinfectant, choose one labelled safe for small animals and rinse well.

These only cover the smell, and they can harm your guinea pigs’ sensitive airways.

When smell can be a health sign

A sudden change in smell, rather than a gradual build-up, can point to a health problem. Watch for:

• A strong smell from one guinea pig rather than from the cage
• A dirty or wet bottom, or diarrhoea
• Blood in the urine, or straining to pee
• Smelly discharge from the eyes, nose or ears

Any of these is worth a vet check. In summer, a soiled bottom also attracts flies, which can cause flystrike.