Blepharitis: This is an inflammation of the eyelids that can cause crustiness, redness, and swelling. It's a common condition often associated with poor eyelid hygiene, meibomian gland dysfunction, or rosacea.

Conjunctivitis: Also known as pink eye, this condition can cause redness, itching, and discharge that may lead to crustiness around the eyelids. It can be viral, bacterial, or allergic in nature.
Eczema (Atopic Dermatitis): This is a chronic skin condition that can cause dry, itchy, and inflamed skin, including around the eyes, leading to redness and possibly crustiness.
Allergic Contact Dermatitis: An allergic reaction to substances like makeup, contact lens solution, or other products used around the eyes can cause redness, itching, and a rash.

Herpes Zoster (Shingles): Although less common, shingles around the eye (herpes zoster ophthalmicus) can cause a painful rash and potentially lead to serious complications like vision loss if not promptly treated.
Keratitis: An inflammation of the cornea that can be caused by infection or injury. It's crucial to diagnose and treat promptly to prevent vision loss.
Orbital Cellulitis: A serious infection of the tissues surrounding the eye that can cause redness, swelling, and pain. It requires immediate medical attention to prevent serious complications.

Sarcoidosis: A condition that can cause inflammation in various parts of the body, including the eyes, leading to uveitis, conjunctivitis, or eyelid swelling.
Lupus: Systemic lupus erythematosus can cause a variety of eye symptoms, including a red, painful rash around the eyes, though this is less common.
Graft-Versus-Host Disease (GVHD): In individuals who have undergone bone marrow or stem cell transplants, GVHD can cause a range of symptoms, including skin and eye problems like conjunctivitis and keratoconjunctivitis sicca.