IGHE and seasonal allergic rhinitis: The first component loaded most strongly on hay fever (r = 0.66), serum total IgE (r = 0.50), skin test reactivity (r = 0.89) and sensitisation to grass (r = 0.69), cat (r = 0.65), and house dust mite (r = 0.71) allergen; the second factor was most associated with asthma (r = 0.67), airway obstruction (r = −0.62), and airway hyperresponsiveness (r = 0.74), whereas the third factor corresponded most strongly to atopic dermatitis (r = 0.90).