It has been suggested to me that he has an 'unhealthy attachment' to [numbers] and I should take away all exposure to them for several weeks
I think it's safe to say that this advice is nuts. IF IF IF his number fascination is a symptom of something (like autism), it's just that -- a symptom, not a cause. Taking it away from him would do nothing to change the underlying issue.
As for whether it IS a symptom of something, I wouldn't be too worried unless you see other signs. As Amylou suggests, a quick check in with your pediatrician may set your mind at ease.
