Medical conditions of the skin, hair, and nails are many. They include eczema, dermatitis, alopecia, hyperhydrosis, keloids, lichen planus, folliculitis, granuloma annulare, molluscum contagiosum, pruritus, herpes simplex, shingles, rosacea, acne, scabies, psoriasis, fungal infections, staph infections, urticaria, keratosis pilaris, neuritis, paronychia, pityriasis rosea, hidradenitis suppurativa, telangiectasia, impetigo, drug reactions, carbuncles, ulcers, lupus, and sarcoidosis. The skin is the largest organ of the body, and various systemic medical conditions manifest first in the skin.