My son is pale in colour all the time he has had asthma 4 3 months?

Pallor not asthma: Pallor is certainly not seen in controlled asthma. If your son were having uncontrolled asthma - coughing, wheezing, labored breathing - not responding well to albuterol - then he might be pale for that episode. Pallor all the time is not likely a result of asthma. So...Are you sure that its asthma? Other lung diseases mimic asthma & may be accompanied by pallor due to a lack of oxygen.

Probably not related: Being pale has many causes but not specifically associated with asthma.