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.
Another condition that causes inflammation of the eyelid is a chalazion. A chalazion occurs when there's a blockage in one of the small oil glands at the margin of the eyelid, just behind the eyelashes. Unlike a sty, a chalazion usually isn't painful and tends to be most prominent on the inner side of the eyelid. Treatment for both conditions is similar.