Your poor cavy sounds like he is in quite as mess. There are 2 main areas that may be causing the problem. Firstly, look at whether the rabbit may actually be the cause of the problem. Perhaps he is making the cavy’s hair permanently wet and this will also inflame the skin. Wet hair will always be attracting dust and food pieces. You could try separating them for a spell to see if this improves.

The second possible avenue of exploration is the bedding. Firstly, is the bedding changed regularly enough? Secondly, is the bedding suitable? Clean the cage every couple of days and replace the sawdust with clean, dry hay. Hay should smell sweet and fresh and not musty.

You can try cleaning your guinea-pig yourself – use warm water and baby shampoo and towel dry afterwards. If his hair is terribly matted, he will need to see a vet to have this removed. He may also need a course of treatment if the skin underneath is inflamed.