Lactose intolerance. which specialist to be consult?

Your family physician will do and will be able to guide you to the right speacialist, if required. In the meantime go through the below links.

http://my.clevelandclinic.org/disorders/lactose_intolerance/dd_overview.aspx
Lactose Intolerance Treatments: Products, Diet, & More
Discovery Health "13 Home Remedies for Lactose Intolerance"

Avoiding milk products helps a lot. I know people having lactose intolerance. They just avoid taking milk products.

Here are some threads which ILites have discussed already on the same topic her in Indusladies

http://www.indusladies.com/forums/infants/35964-lactose-intolerance-advice-please.html
http://www.indusladies.com/forums/health-issues/6553-lactose-intolerance.html

You may use the search option here as many of the things are already discussed and thus reduce your waiting time for getting a response.