Blepharitis is a common condition that causes inflammation of the eyelids. Blepharitis is often associated with overgrowth of bacteria or a parasite known as demodex on the eyelashes or eyelid margins. Blepharitis can affect people of all ages and is often associated with certain skin conditions including acne, rosacea and seborrheic dermatitis. Common signs and symptoms of blepharitis include chronic irritation, redness of the eyelid margins and crusting of the eyelashes (particularly in the morning).