Effects and side effects of calamansi Calamansi is a citrus fruit native to Southeast Asia and widely used in the region as a spice, flavoring agent, and traditional medicine Here is an overview of nine possible benefits and side effects of calamansi, as well as some tips on how to eat it: Table of Contents 1. Immunity Booster 2. Digestive Aid 3. Skin Care 4. Weight Loss 5. Oral Health 6. Respir..