What causes swollen skin around a dog's eye?

The first thing to do is, simply, take it to the vet. The vet can determine whether the problem is being caused by mites, fleas, stress, dietary, or an allergy and general sensitivity. Under no circumstances should you try to treat the problem with human remedies. There would be some treatments available at a pet store, but you could well be wasting your money by not investigating the problem properly.

Problems that recur are likely due to contact with a specific allergen or a type of food. In this case, you must try one thng at a time. Keep the dog on a specialised diet that is proven to be low in ingredients that can cause a reaction. After several months of this, if the problem recurs it is likely to be environmental. Certain plants can trigger such a reaction, as can other common household items such as certain cleaners, carpets or other floor surfaces.