Hair thinning and diffuse hair loss result in low density hair appearance. These include female pattern hair loss, telogen effluvium, and loose anagen syndrome. 

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Hair loss that causes bald patches is either scarring or non-scarring. Scarring alopecia include folliculitis decalvans, lichen planopilaris, frontal fibrosing alopecia, ccca,  pseudopelade, scleroderma, and lupus erythematosus. The non-scarring alopecia include alopecia areata, tinea capitis, trichotillomania, and physical causes of hair loss.

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Scalp problems include those causing pruritis (lichen simplex, acne miliaris necrotica, pediculosis capitis), those that affect the sebaceous glands (seborrhea oleosa, and seborrheic dermatitis), and those causing scaling (pityriasis capitis, psoriasis, pityriasis amiantacea).

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Hair shaft problems result in hair breakage (includes bubble hair, trichorrhexis nodosa).