In case of food intolerance (e.g. enzyme deficiency), the immune system is not (or almost not) involved in the reactions. “Allergy to lactose” is therefore an improper wording, adverse reaction to lactose (diarrhea, etc.) should be named “lactose intolerance”.
Lactose intolerance is due to the absence or a metabolic deficiency of the lactase enzyme (disaccharidase of the intestinal brush border). If not hydrolyzed, lactose cannot be absorbed in the intestine. Therefore, the bacterial flora transforms this disaccharide, through a fermentation process, in short chain organic acids and gas. This fermentation can lead to abdominal pain, flatus, bloating, loose stools or watery diarrhea. To manage lactose intolerance, lactose should be avoided in the diet1.
So, for infants who are suffering from a lactose intolerance, it is recommended to feed them with a lactose free formula, and as such a rice-based formula can also be used in the management of lactose intolerance.