A 28-year-old woman from Mumbai presents with a 3-year history of recurrent itchy rashes on her hands, wrists, and face. She reports that symptoms worsen during winter and improve in summer. On examination, the affected areas show erythema, lichenification, and excoriations. She denies any contact with known irritants at work. Prick testing for common allergens is negative. Her 5-year-old daughter has similar skin lesions. Which of the following is the most important pathophysiological mechanism underlying her condition?