Cat allergies are easy to spot once you know what you are looking for.
An ear infection can be detected by the constant shaking of their heads which is not normal.
On closer inspection you should be able to see that the outer part of their ears should be pink and fairly flat.
If there are any signs of swelling or toughening then the chances are they have a blood clot or an allergy.
Also you can also look around the ear to check for black debris which indicates mites.
If there are mites you should clean them out by using a 50/50 mixture of vinegar and water.
Use cotton wool to slowly get rid of all the black debris and make sure all is clear as there may be a good chance it will resurface again if you have not cleared everything thoroughly.
You can also try a different remedy of soaking garlic in olive oil for 12 hours and using them as drops into their earlobes.
If you put six drops twice daily for 8 days this should clear up any unwanted build up of parasites.
To check for any cat allergies in their eyes you should look at the surface of them to check if they are clear and not cloudy.
Signs of developing cataracts are cloudiness and non-constricting pupils when you shine a light of them.
Liver disease can be detected by looking at the whites around the cornea.
Finally if they are yellow then get them checked out as soon as possible.