The swelling under your eyes could potentially be caused by a variety of factors, but it is most likely due to an allergic reaction. If you have not eaten any new foods or used any new products on your face or eyes recently, it may be related to something else. If the reaction seems to be recurring, you could try using Benadryl™ and reassessing any changes in your routine or diet in the past few days. Otherwise, there is no immediate need to take any action at this time.