Some patients do experience more swelling under the eyes after IPL. I am one of them. It seems to happen more frequently in patients with diffuse redness pre-treatment more than in those with mainly brown spots or larger veins. It is also more common in patients with thin skin, or those who have been on tretinoin. Usually it resolves in 3-5 days, but rarely I have seen it last as long as 7-10 days.
For those patients who are more prone to swelling, and for myself, we have found that pre-treating with Prednisone the morning of the treatment (3-6 hours before treatment) and applying cold packs immediately after treatment reduces the swelling pretty dramatically. We also recommend those patients sleep on an extra pillow the night after treatment, and until the swelling resolves.
And be sure you are wearing a broad spectrum UVA/UVB sunscreen daily, and avoid sun exposure for 3 weeks before treatment.
I have never seen it increase lines under the eyes, except temporarily for a couple of days.