The first two wave types, P and S , are called body waves because they travel or propagate through the body of Earth. The latter two are called surface waves they the travel along Earth's surface and their amplitude decreases with depth into Earth.
The causes are many and can have bacterial infection, seborrheic dermatitis of the face or even a scalp, rosacea, allergies, and in very rare cases, the lice. If the itchy eyelids is brought about by seborrheic dermatitis then you may develop dry, flakey patches of skin on the eyelid.
Most often, eyelid edema is caused by allergic reactions to products such as eye makeup or eye drops, or allergens such as pollen. While most causes of eyelid edema are not dangerous, this condition can also be a symptom of trichinosis, a disease caused by eating undercooked meat, and other serious infections.