What is an eye stye? An eye stye can occur on the outside or inside of eyelids. They are pus filled and painful. They are also very common in occurrence. It is caused due to a blockage of the one or more sebaceous glands in the eye. This blockage could be because glands in the eyelids get obstructed with scar tissues or foreign substances like make up products. It might progress to an infection of the eye stye with bacteria called staphylococcus. Symptoms of an eye stye are presence of a red and tender swelling near the edge of the eyelids.https://www.youtube.com/watch?v=FMvkxwRSH6s