A red pimple on the edge of a dog's eyelids may be caused by mosquito bites, parasitic infection, or third eyelid hyperplasia. It is best to check whether there are parasites on the dog first, and confirm whether the dog has been taken for mosquito control recently. If there are many places where there are mosquito bites or parasitic infections, you can apply anti-inflammatory ointment. If it is third eyelid hyperplasia, it is best to perform surgery in time to avoid affecting the dog's health.