Judy,
How is this mom handling the normal "cluster feeds" in the evening?  Could the
baby be suffering from a relative lactose overload?  Frequent breast switching
might cause gas, but frequent breastfeeding increases prolactin levels, which
increase the rate of all the reactions producing the major components of milk-
including fats.  Therefore, frequent nursing (as long as the baby is allowed
to stay on one breast long enough to get the hindmilk) will increase the
amount of fat the baby gets relative to lactose, and decrease gas.  I have
found that a lot of this nightime gas is either hunger (moms don't understand
that babies eat and sleep in clusters, and try to hold them off); or
overfeeding, by bfing by 'the clock' the baby gets mostly foremilk, which
leaves a caloric deficit, which makes the baby want to eat, which overfills
the stomach with more low calorie milk.  Then the 'extra' lactose gets
metabolized by bacteria, creating gas. Woolridge wrote a lot on overfeeding
syndrome.  Try suggesting just bfing on one breast per feeding until baby lets
go spontaneously, then offering the other.
        I would not discount the possibility of allergy, either, but it is
always good to try to most common, least interventive strategy first.  "When
you hear hoofbeats, don't expect zebras" we say in the US. How's that for a
culturally biased platitude?
Catherine Watson Genna, IBCLC