Morgellons disease is a rare skin condition that causes a variety of symptoms, including: Skin sensations: Crawling, biting, or stinging sensations on or under the skin Skin lesions: Sores or rashes that may be itchy and appear suddenly Fibers: The belief that fibers, threads, or black stringy material are in or on the skin Fatigue: Severe fatigue Concentration: Difficulty concentrating Memory: Memory loss Mood: Depressed mood Other symptoms include: Sores that leave red scars Feeling like bugs are crawling on the skin Burning or stinging sensations under the skin