there are two reasons for this. the most common reason is nasolactrimal duct obstruction -- the tear duct drainage system from the eye to the nose is clogged or compromised. this tends to spontaneously improve as the child ages and can be surgically fixed if it does not clear or open by age 12-18 months. another reason could be a minor eye infection like conjunctivitis. if the eyes are not red and the mucous is not pus then the most likely cause is the nasolactrimal duct obstruction. your baby will see his pediatrician at age four months so assuming this is not an infection it can wait until then.
3 month old infant has dry crusty mucus around his eyes when he wakes in the morning. should he see a doctor?