"Almost all oral solids (92.8%) contain at least one potential allergen"
Source: attached journal article.
"... intolerances to an inactive ingredient can cause symptoms through mechanisms such as malabsorption, which causes gastrointestinal symptoms via direct osmotic effects or as a result of their fermentation in the digestive system. These potentially affect a much larger population with more benign symptoms compared to allergic reactions"
Source: attached journal article.
Attached a popular article from Science News as well as the original journal article.