Hair diseases are conditions affecting the hair follicles or scalp. They're mainly grouped into:

Hair Loss (Alopecia): Includes pattern baldness (genetic), alopecia areata (autoimmune patches), and telogen effluvium (stress-related shedding).

Scalp Conditions: Involve skin issues like dandruff, seborrheic dermatitis (greasy, scaly skin), psoriasis (silvery plaques), and ringworm (fungal infection).

Hair Shaft Disorders: Problems with the hair fiber itself, like trichorrhexis nodosa (brittle nodes from damage) or monilethrix (genetic "beaded" hair).