Does sleeping on your stomach cause eye bags?

Yes: Sleeping with your head lower than your body increases fluid accumulation in the head, including the eyelids.

No: The "bags" are caused by fluid collection around the fatty protective layer under the eyes and position does not have a lot to do with it. As we get older these area often enlarge due to age, gravity and thinning of the layer over the fatty tissue. This can be corrected by cosmetic surgery.

No: "bags" under the eye represent many things-- swelling, orbital fat prolapse, skin laxity. Swelling due to allergy can be treated. Most other causes of "bags" under the ey are amenable to surgical correction.

Dermatochalasis: Laxity of the connective tissue around the eye that causes the fat pads around the eyeball to "push" forward called dermatochalasis. This can occur with age. Skin laxity or "looseness" also causes this. Surgery is the only option. You should see your doctor. Another cause is allergies. If you have itching and nasal congestion try cold compresses and antihistamines.