I agree with Mary. There is no connection between LI and allergies. No 
research supports a connection. And there are no physiological pathways by which a 
connection is meaningful.

Many people are LI. Many people have allergies. Naturally there will be an 
overlap. However, there is no causal effect in either direction.

She is also correct that a large meal will "buffer" the lactose. In addition, 
people can often have more lactose than they suspect without significant 
symptoms.

One mouthful should not produce strong and rapid symptoms in any case. That's 
more likely to be a psychological reaction than a physical one, since it 
takes time for the undigested lactose to move through the intestines. What you may 
be experiencing is the gastrocolic reflex, "an increase in intestinal and 
colonic peristaltic activity following entrance of food into the empty stomach." 
This is thought to be a sign of irritable bowel syndrome, and there is a 
correlation between LI and IBS.

Steve Carper
Steve Carper's Lactose Intolerance Clearinghouse
www.stevecarper.com

Planet Lactose Blog
planetlactose.blogspot.com