We estimated the relationship between cumulative exclusive breast-feeding up to 6 months and wheezing , rash and body mass index ( BMI ) at 12 months [ in the Whistler cohort ( n = 494 ) and PROBIT ( n = 11,463 ) ] , and wheezing , rash , asthma , hay fever , eczema , allergy and BMI at age 6.5 years ( PROBIT ) .