Red and swollen dog eyelids are caused by many reasons, generally including the following points:

1. Eye injuries or insect bites: This can happen if the dog accidentally touches its eyes during play or activities, or is bitten by mosquitoes, bees, etc.

2. Allergic reaction: caused by dogs coming into contact with irritating substances, such as certain foods, sprays, etc., which can also cause redness and swelling of the dog's eyes.

3. Eyelash barbs: It may be that the eyelash barbs around the dog’s eyes have stimulated the dog’s eyes to become red and swollen.

4. Inflammation: When our pet owners often feed our dogs greasy and difficult-to-digest food, it may also cause the dog’s eyes to become red and eye feces to increase.