My 2 year old has pink bags under his eyes. what causes this?

"Allergic Shiners": can look pink or purple, especially if he has nasal congestion or tearing. It's more likely in older kids, but one of mine got them at 2 when I brought home a beagle. Local irritants like soap & lotion can redden the skin under the eyes. If the mucous membranes of his lower eyelids are inflamed & " gunky", he could have "pink-eye", which is often viral but warrants a visit to his pediatrician.