Hyperpigmentation is caused by an overproduction of melanin, leading to darkened skin. Factors such as mechanical friction (intertrigo), hormonal changes (e.g., pregnancy, PCOS), genetic predispositions, insulin resistance (e.g., acanthosis nigricans), obesity, and UV rays contribute to this condition. This triggers hyperkeratosis, a thickening of the skin due to excessive keratin production. As a result, dark areas can develop in various regions, including the underarms, groin, inner thighs, elbows, knees, neck, and beneath the breasts.