There is no possible physiological route that would lead to symptoms from 
hand contact with pure lactose. Lactose intolerance comes only from the lack of 
digestion of lactose. Lactose cannot go through the pores to the bloodstream 
and if it did by magic absolutely nothing would happen because of it. It's 
extremely unlikely that you could get enough into your system by swallowing powder 
that floated through the air, either.

It is possible to have a reaction to dairy proteins through contact, however. 
If you're making a formula then you probably have dairy proteins in it 
totally separate from the lactose. Would enough dairy proteins be present in the 
wafting of the powder to cause a reaction? Probably not. If you could be affected 
by that small an amount of protein then you would know it by now because you 
would be reacting all the time to traces of dairy. And you wouldn't get 
digestive symptoms that could be confused with lactose intolerance, but rashes and 
other skin problems.

So - most likely it's just a coincidence, or even a psychological affect from 
the knowledge that you're handling lots of lactose.

Steve Carper
Steve Carper's Lactose Intolerance Clearinghouse
http://ourworld.compuserve.com/homepages/stevecarper

Planet Lactose Blog
http://planetlactose.blogspot.com