According to the Mayo Clinic website, lactose intolerance, alternately called lactase deficiency, “means you aren't able to fully digest the milk sugar (lactose) in dairy products. It's usually not dangerous, but symptoms of lactose intolerance can be uncomfortable.”
The website goes on to explain that the real issue for lactose intolerant people is “an enzyme produced by the lining of your small intestine. Many people have low levels of lactase, but most don't experience signs and symptoms. Only people with both low lactase levels who also have associated signs and symptoms have, by definition, lactose intolerance.”
The TLC website, HowStuffWorks.com, says 30 to 50 million Americans suffer from a lactose intolerance condition and when they indulge in dairy delights like cheese, cream, and milk can cause gas, bloating, cramping, and an all-around uncomfortable state.
But, the website states, this condition is not necessarily a milk allergy.
https://www.empowher.com/lactose-intolerance/content/scream-ice-cream-ins-and-outs-lactose-intolerance