Hello , my 2 year old son started getting sleep in his corner of eye today and I kept cleaning it out but it kept coming back it s the corner closer to nose and it s a yellow colour quite thick but since being in bed he s been rubbing his eyes and both eyes are very watery and gooey but not flakey or crusty just very watery and sticky mainly over the eyelashes but he hasn t been in contact with anyone recently who s been ill he s very happy and healthy and he s had nothing different to cause an allergic reaction what could this be as I m worried thank you