Dr. Greene's Answer
The theory that babies have to be at least 2 years old to get allergies is still very common. Because the presence of allergies represents an overactive immune system, and because babies’ immune systems don’t reach normal functioning until age 2, it was thought that they couldn’t get allergies before then. Now we know that the immune system doesn’t develop evenly and that allergies can indeed be present in very young babies.
Both pinkeye (conjunctivitis) and allergies can make the eyes red. With pinkeye, however, there is goop in and around the eye, especially after sleeping. Often the amount of redness between the two eyes is not symmetrical. When allergies are the cause, the effect on the two eyes is usually symmetrical. With allergies, the eyes are puffy and itchy and if there is any discharge, it is usually clear and thin. Without goop or crusty stuff, it’s most likely not pinkeye and the possibility of allergies should be looked into.
One interesting note on pinkeye–for nursing moms, a drop of breast milk in the baby’s eyes often has enough antibacterial activity to treat the pinkeye without antibiotics. This approach is much gentler.