What Causes Watery Eyes With Red Mark Under Eyes?

Hello. My 6 year old came home from school today and mentioned her eye had been tearing at times throughout the day. I questioned if she might come down with something as her three year old brother has a cold. Soon after, however, she had a red mark under her eye. She admitted she had rubbed the area. Within 3 hours, her one eye became quite weepy, and the mark became quite red (with no additional rubbing). She indicated it hurts if it is touched. She does not have a temperature. She did not eat anything unusual, or use any new soaps or lotions. Any thoughts what this may be or how I can help her?