Is it allergies or something more serious?

My dog suddenly has puffy eyelids (particularly the lower ones). He is 8 and has never displayed this symptom before. He is not clawing at his eyes or showing any distress. His nose is cool and moist. He does not seems to have other symptoms. This came on suddenly after he went out in the back yard. He is 1/2 Dalmatian, which I mention because they can be allergy-prone. I can’t find much help on the Web.