Can you tell me exactly when is the earliest asthma can be diagnosed in a baby?

Hard to say. Many things trigger asthma like wheezing in infants:rsv, other forms of infectious bronchitis or bronchiolitis, so confidence using the label is hard.As many as 75% of wheezing infants will grow out of their recurrent pattern of wheezing by age 5, and it makes using the term imprecise at best.Males with bad asthma are often evident by 1 yo and females by 4, but i rarely use the label before 5.
Asthma. Children under the age of 5 who have symptoms suggestive of asthma (cough/wheezing/etc) will be treated as if the are asthmatics while other diagnoses are being excluded. Because this particular population of patients can not always participate in some of the diagnostic tests, there is reluctance to give children under the age of about 5 a diagnosis of asthma.